In-Depth Damage Guide

General Damage Formula

This section covers the structure of the general damage formula used to calculate the damage you see in-game. Each section of this guide refers to sections of this formula and explains how it functions in detail. The general formula can be described in the following way:

The following is a more math-focused version of the damage formula and includes the math of each respective multiplier:

This is just average damage without including variance and without including attack speed. Damage values in Diablo 4 have quite a significant range, which means you see values far higher and lower than the calculated average damage. You can find more information about this in the variance Section. The final part of the formula accounts for Enemy Damage Reduction, which may be replaced by [0.02] if you are level 60.

The damage formula changes slightly when we look at flat damage effects such as X'Fal's Corroded Signet or Thorns. The part that changes is that the [Average Weapon Damage] and [Skill%] multipliers are removed and replaced with [Flat Damage]. As of Season 4, flat damage sources like X’fals now have weapon damage scaling in the damage value seen on the item, which means that [Flat Damage] is the damage value you see on the item or the Thorns total you have on your character.

Multiplicative Damage Sources

The term "Global Multipliers" is used in the general damage formula and it is quite simply just that, a multiplier to all your damage dealt as long as the condition is met. Some have the condition that the target must be poisoned, while some require you to cause a critical strike. These multipliers are generally identified by having [x]% in their tooltip, such as the unique effect on The Grandfather. All of these are multiplied together and are included in the damage formula in the following way:

Global Multipliers are largely independent of your stats from items and paragon points and, as such, do not increase the amount of stats you have. For example, you have a [x]30% multiplier vs Frozen enemies from Frigid Finesse regardless if you have [+]0% Damage vs Frozen enemies or [+]300000% Damage vs Frozen enemies. However, certain skills, passives, and legendary paragon nodes may have increased effectiveness by having more of a specific stat. One example is the Precision keystone passive for rogues, which scales in strength based on your [+]Critical Strike Damage%.

Due to how percentages work, we have to make sure that we add a +100% as a base so that the multipliers become an increase of the appropriate percentages. To use a practical example, if you have Malice, Frigid Finesse: Frozen, Weapon Mastery: Crossbow, and Enhanced Dash, then your total damage increase from the global multipliers would be:

To know what global multipliers affect your build and skills, you must either test it yourself or refer to relevant build guides. For example, despite Weapon Mastery: Swords stating that you deal [x]% more damage, it does not increase the damage of Poison Imbuement You would not learn this information from reading the tooltips, it is something you would have to test yourself to verify.

Additive Damage Multiplier

The Additive Multiplier is the sum of all stats commonly referred to as "additive". The stats on your items with  [+]% are additive bonuses and added together into their associated multiplier (also known as “bucket”). To list a few of the stats belonging to the additive multiplier, we have Close Damage, Distant Damage, Core Skill Damage, Damage vs ..., Damage to ..., Vulnerable Damage, Critical Strike Damage, and Overpower Damage (more on the last 3 later). There are two important prospects to remember when it comes to these additive stats, the first is that their value entirely depends on how frequently their condition is met, and the second is something called diminishing returns.

First, regarding conditional damage bonuses, if you compare +30% Close Damage with +60% Vulnerable Damage, it may look like Vulnerable Damage would be the way to go because the number is larger. However, let's say you only have 10% uptime on Vulnerable and are always near your target. In this context, Close Damage would still be worth +30% additive damage, while the +60% Vulnerable Damage averages to +6% Additive damage. Uptime, meaning how frequently the condition is met, matters when you assess how valuable an additive stat is.

The second prospect, diminishing returns, is one of the most important concepts when optimizing your damage. For example, adding +60% additive damage when you have no additive stats compared to when you have +800% additive damage already gives vastly different results. If you have no additive damage bonuses, the additive multiplier has a base “100%” for the same reason described in the multiplicative damage section. If we add +60% additive stats to our additive multiplier, we get 100%+60% = 160%. To calculate how much of a gain this is, we can calculate the relative increase using the following formula:

Based on the example values listed above, we would then put (100%+60%)/(100%) = (160%)/(100%) = 1.6. This means that 160% is 1.6 times as large as 100%, and we deal, as such, 1.6 times more damage.

Comparing this gain to if we added another +60%, our formula would be the same but the values would change. Our Old Additive Multiplier would be 160%, and our New Additive Multiplier would be 160%+60%. (160%+60%)/(160%) = (220%)/(160%) = 1.375. In other words, adding another +60% means our damage increases by 1.375 (37.5%)  and not 1.6 (60%) as it did the first time we added +60% additive damage. This is called diminishing returns. 

To optimize your damage, you must understand this concept as certain builds have over +2000% additive damage. So adding another +60% Close Damage would only be an increase of:

(100%+2000%+60%)/(100%+2000%) = 1.0285... = 2.85% increased damage

In other words, if you add +60% Close Damage when you already have +2000% additive damage, you would only see a 2.85% overall increase to your damage dealt.

Relative Damage Gain

When optimizing your damage output, you may ask yourself “Is option A better than option B”? We can verify this by analyzing the damage multipliers using the relative gain formula we just mentioned. For example, you may wonder if a [x]10% multiplier is more of a damage increase than [+]200% unconditional Additive Damage. To assess this, you first calculate the sum of all additive stats before adding [+]200%. Assume you have [+]1000% Additive Damage from stats and paragon points. You then make use of the Relative Gain formula from earlier:

It may be easy to understand that multiplying your damage output by 10% causes you to deal 10% more damage. However, it may not be as clear that adding [+]200% Additive Damage in this example would be an 18.2% increase. In situations where you may wonder if [+]Main Stat, [+]Additive Stats or a [x]% Global Multiplier adds the most damage, you may also use the Relative Gain formula. Let us assume that you have 700 Main Stat, [+]850% Additive Stats, and you want to know if [+]130 Main Stat, [+]200% Additive Stats, or a [x]10% Global Multiplier results in the highest damage gain. You could then do the following calculations:

In this example, it is clear that adding [+]200% unconditional Additive Damage results in the highest damage gain. However, when comparing setups with multiple factors and changes in several or all multipliers, it is required to include all the multipliers in the comparison, instead of analyzing just one. For this, we use something like the following formula:

If the answer is greater than 1, Set 1 is the more optimal setup, while if the answer is less than 1, Set 2 is the more optimal setup. This is great for situations where you compare weapons, where several multipliers are affected by the choice.

When are other stats equal to Global Multiplier?

Sometimes, you will run into a situation where it is more convenient to calculate how much a specific stat is worth compared to the damage increase of a Global Multiplier. As a general rule of thumb, a Global Multiplier is often worth more than the relative gain you would see from adding other stats in the endgame, but it is not always obvious. You can calculate precisely how much, for example, [+]Additive Damage would be equal to a [x]% global multiplier using the following formula:

So, assuming you have [+]1000% Additive damage from stats and paragon points and want to compare it to a [x]10% Global Multiplier. We can calculate that 1.1 x (100% + 1000%) - (100% + 1000%) = 110% Additive damage, in this example, equals the gain of a [x]10% global multiplier. This works for other multipliers too, such as Main Stat. All you have to do is change the [Additive Multiplier] to the [Main Stat] multiplier.

Vulnerable Damage

Vulnerable Damage is dealt when you damage a target affected by Vulnerable, a condition applied by certain skills and effects. As of patch 1.2.0, [+]Vulnerable Damage% was changed from being added to a separate multiplier to a conditional additive stat in the additive multiplier. In other words, [+]Vulnerable Damage% is now comparable to Close Damage and other conditional additive damage stats. Additionally, there is a separate multiplicative damage bonus when you hit a Vulnerable target of 20%[x]. This multiplier cannot be increased by any means and is applied to the damage calculation as a global multiplier.

What we do to circumvent this issue is that we use the bottom value of the tooltip exclusively. We add the bottom value to our additive multiplier and then multiply our total damage by [x]20% due to the Vulnerable multiplier when damaging a Vulnerable target. We do the same with all other global multipliers with Vulnerable conditions such as Malice, Weapon Mastery: Bow, and others.

Math Behind Top Tooltip Value

The top value, 76.4%, is inaccurate in damage optimization contexts as the percentage is not a correct representation of how it affects your damage dealt. The top value is calculated using the following formula:

(100% + [+]Vulnerable Damage% from items and paragon) x 120% - 100%
In this case: (100% + [47%]) x 120% - 100% =  76.4%

This implies that, when we hit a Vulnerable target, we do 76.4% more damage when compared to if the target was not Vulnerable. Again, we want to emphasize the fact that this is inaccurate. We can use what we have learned about the additive multiplier to test this. Let us assume that we have [+]1000% additive damage in total, we would get the following damage gain if we then add [+]47% Vulnerable Damage:

Damaging a target that is not Vulnerable: (100%+1000%) = 1100%

Damaging a target that is Vulnerable: (100% + 1000% + 47%) x 120% = 1376.4%

Relative gain: 1376.4%/1100% = 1.2512 = 25.12% increased damage

In other words, when we added [+]47% Vulnerable Damage and the x1.2 multiplier, we gained a relative increase of 25.12%, not 76.4% as the tooltip suggested. The issue with the top tooltip value is that it becomes difficult to understand how much certain skills, passives, and aspects affect your total damage. For example, Rogue has a passive called Malice. Rank 3 of Malice changes the Vulnerable tooltip in the following way:

(100% + [Vulnerable% from items and paragon]) x 120% x 109% - 100%

In this case: (100%+[47%]) x 120% x 109% - 100% = 0.92276 = 92.3% even though it is simply a conditional damage multiplier with the condition that the target is Vulnerable.

Critical Strike Damage

Critical Strike Damage (henceforth CSD) is done when your damage causes a Critical Strike. As of patch 1.2.0, [+]Critical Strike Damage% (henceforth [+]CSD%) was changed from being added to a separate multiplier to a conditional additive stat in the additive multiplier. In other words, [+]CSD% is now comparable to Close Damage and other conditional additive damage stats. Additionally, there is a separate 50%[x] multiplicative damage bonus when you cause a Critical Strike. This multiplier cannot be increased by any means and is applied to the damage calculation as a global multiplier. Do note that generally speaking, Damage over Time effects cannot critically strike, but there are unique situations, such as Blended Poison Imbuement, which causes Critical Strike Chance to have value for Damage over Time builds.

Damage Value of Critical Strikes

It is important to note that the value of Critical Strike Damage is relative to the amount of Critical Strike Chance (henceforth CSC) you have. The formula to calculate the average damage done per hit including CSC is divided into two parts. The first part is [1 - CSC] x [100% + Additive Stats], which is how much damage you do when you do not cause a Critical Strike. The second part is [CSC] x [100%+Additive Stats + [+]CSD%] x [100% + [x]%CSD], which is how much damage you do when you cause a Critical Strike. The [100% + [x]%CSD] multiplier is the product of all the global multipliers with Critical Strike Damage bonuses. Combined, it becomes the following:

So in a scenario where you would compare adding [+]100% unconditional Additive Stats or [+]150% CSD% if you had 40% CSC, you would have to do the following calculations:

Average Damage + [+]100% unconditional Additive = [100% - 40%] x [100% + 100%] + [40%] x [100% + 100% + 0%] x [100% + 50%] = 2.4

Average Damage + [+]150% Critical Strike Damage = [100% - 40%] x [100% + 0%] + [40%] x [100% +0% + 150%] x [100% + 50%] = 2.1

Because 2.4 > 2.1, it would be better to add [+]100% unconditional Additive Stats compared to adding [+]150% CSD%. The math would work out similarly regardless of the [+]Additive Stats and [+]CSD% we would have initially. However, there is a convenient way to calculate the relative value of [+]CSD% compared to unconditional Additive Stats, and it is with the following formula:

Using this formula, we can see that if we have 40% CSC and a [x]%CSD of 50%, we get: 100% - [(100% - 40%)/(100% + 40% x 50%] = 100% - 50% = 50%. So [+]CSD% is worth 50% of unconditional Additive Stats. Let us try this theory by plugging in [+]200% CSD% in our average damage calculation with the same context as before:

Average Damage + [+]100% unconditional Additive = [100% - 40%] x [100% + 100%] + [40%] x [100% + 100% + 0%] x [100% + 50%] = 2.4

Average Damage + [+]200% Critical Strike Damage = [100% - 40%] x [100% + 0%] + [40%] x [100% + 0% + 200%] x [100% + 50%] = 2.4

This formula works for all damage conditions where we have [+]% and [x]% damage bonuses with the same condition. If we, instead, wonder how much damage additional [+]CSD% would give us, we can use the relative gain formula shown in the Additive Damage Multiplier section.

Math Behind Top Tooltip Value

What we described above for the Vulnerable damage tooltip applies here, meaning that the top value is misleading regarding understanding how Critical Strike Damage affects your damage. The top value is calculated using the following formula:

(100%+[critical strike damage% from items and paragon]) x 150% - 1

In this case: (100%+[410.1%]) x 150% - 100% = 665.1%

This implies that, when we score a critical strike, we do 665.1% more damage compared to a non-critical strike. Again, this is not accurate. We can use what we have learned about the additive multiplier to test this. Let us assume that we have +1000% additive damage in total, we would get the following damage gain if we then add +410.1% critical strike damage:

Dealing a non-crit: (100%+1000%) = 1100%

Critical strike: (100%+1000%+410.1%) x 150% = 2265.15%

Relative gain: 2265.15%/1100% = 2.059 = 105.9% increased damage

As we can see, adding +410.1% critical strike damage and the [x]50% CSD multiplier to your damage calculation is a relative increase of 105.9% and not 665.1% like the tooltip suggested in this case. In real situations, we use the bottom % on the tooltip in damage calculations and the [x]50% CSD multiplier as a separate global multiplier with the condition that you critically strike.

Overpower Damage

Overpower Damage (henceforth OPD) is a conditional damage modifier that turns your damage value cyan for non-critical strikes, and orange for critical strikes. Overpower has a set 3% probability of occurring normally, but certain skills, passives, and aspects can guarantee that a skill Overpowers. Unlike Critical Strikes, attacks Overpower per cast rather than per hit, meaning that abilities with multiple hits in one cast Overpower for each hit.

[+]Overpower Damage% (henceforth [+]OPD%) is a conditional additive stat in the additive multiplier. In other words, [+]OPD% is comparable to Close Damage and other conditional additive damage stats. You are also given [+]OPD% based on your current HP and Fortified life (see formulas and calculation below). For example, with a base HP of 400 and a maximum HP of 4400, we should add another [+]1100% Overpower Damage to our additive multiplier.

As of patch 1.2.0, there is a separate 0%-50%[x] multiplicative damage bonus when you Overpower that scale depending on your current health (with 50% being the max when you are at full health). This multiplier cannot be increased by any means and is applied to the damage calculation as a global multiplier. Do note that Damage over Time effects and Channeled abilities cannot Overpower under any circumstance.

Formulas Behind Overpower Calculations

The [x]50% Overpower Multiplier is calculated based on your current health when you deal Overpower damage with the following formula:

Overpower Multiplier = 100% + 50% x (current HP/Max Life)

So if you have 50% HP, your multiplier would be: 100% + 50% x (50%/100%) = 125% = [x]25%

As we mentioned in the Vulnerable and Critical Strike Damage sections, it is important to understand that the tooltip values are misleading. The top value is calculated using the following formula:

(100% + [+]Overpower% from items and paragon) x 150% - 100%

In this case: (100% + [219.8%]) x 150% - 100% = 379.7%

However, Overpower is suffering further from the misleading tooltips as the bonus [+]OPD% you get from Health and Fortified is not shown on the tooltip. You get +1% Overpower Damage for each 1% of your Current Life that exceeds your Base Life and you get +1% Overpower Damage for each 1% of Fortified Life. That means, if you are fully Fortified with 4400 Max Life and 400 Base Life, you get the following extra [+]OPD%:

[+]Overpower Damage from HP = [Max Life - Base Life] / [Base Life] = [4400-400] / 400 = 1000%

[+]Overpower Damage from Fortified = [Current Fortified Life] / [Base Life] = 4400 / 400 = 1100%

Total [+]Overpower Damage from HP and Fortified = 1000% + 1100% = 2100% [+]Overpower Damage

So whenever we cause an Overpower attack, with a base HP of 400 and a fully Fortified Max HP of 4400, we should add another [+]2100% to our additive multiplier, which the game does not show us in the form of a number in the tooltip. So to accurately assess how much damage your Overpower attacks do, add the bottom [+]% of the tooltip to your calculation and convert your HP into [+]OPD%. Also, remember to multiply your damage with the [x]50% Overpower multiplier (presuming you are at max HP).

Main Stat

Each class has a main stat that gives them something called skill damage. The main stats Necromancers and Sorcerers use are Intelligence, Rogues and Spiritborns use Dexterity, Barbarians use Strength, and Druids use Willpower. The main stat damage contribution can be deceiving due to its wording in the tooltip. If you hover over your main stat on your character sheet, it shows the following:

This functions as a separate multiplier and is not to be confused with skill%. In other words, in the damage formula, skill% and Main Stat function as two separate and completely independent multipliers. Another misleading aspect is that despite being called Skill Damage, Main Stats increase the damage of effects such as X'Fal's Corroded Signet, Thorns, and other Flat Damage effects. Because 1 main stat is 0.1% Skill Damage, dividing your main stat by 1000 correctly converts your main stat to a percentage (1/1000 = 0.001 = 0.1%). That means we can use the following formula to convert your main stat to a percentage:

As of Season 5, each class has unique scaling from Main Stat. This implies that 1% Skill Damage is now different and not 10 Main Stat as it used to be. Below is a list with the new Skill Damage% scaling for each class.

• Druids, Necromancers, Sorcerers, and Spiritborn gain 1% Skill Damage per 8 Main Stat
• Rogues gain 1% Skill Damage per 9 Dexterity,
• Barbarians gain 1% Skill Damage per 10 Strength.

This change means that when you calculate your damage gain from your Main Stat, you change the "1000" in the formula above to 800 if you are a Druid, Necromancer, or Sorcerer, and to 900 if you are a Rogue or Spiritborn. In the damage calculation formula, this is the Class Coefficient.

Because your main stat increases your Skill Damage by xxx.x%, we need to make sure that our main stat multiplier includes a base 100%. Without it, if we put 56.2% Skill Damage into our formula, it would mean we do less damage if we have between 0% and 100% Skill Damage, which is incorrect. As such, our [Main Stat Multiplier] is equal to [100% + Main Stat %] in the damage formula.

Weapon Damage

The damage you deal from skills and effects is based on your weapon, and as of Season 4, flat damage aspects also scale with your weapon damage. Weapons in Diablo 4 have a damage range, which means your damage varies between a minimum and maximum value. Additionally, weapons are not all made equal, let us look at the following example:

Notice how the Damage per Second (henceforth DPS) is practically identical even though the damage range differs. This is important for builds that aim to one-shot bosses or do the most damage in as few attacks as possible. To calculate the average weapon damage, you use the following formula:

Average damage for Glaive: (419+629)/2 = 524

Average damage for Polearm: (466+698)/2 = 582

If we compare the average damage for the Polearm and Glaive, we get 582/524 = 1.1106 or an increase of 11.06% damage for the Polearm. We can also calculate the difference in Attacks per Second (henceforth ApS), which you can find underneath the damage range. Glaives have 1 ApS and Polearms have 0.9 ApS, and the difference between the two is calculated by taking 1/0.9 = 1.1111, or an increase of 11.11% ApS. This means that in a long fight, the DPS for the two weapons would be close to identical from base damage and ApS perspectives. 

Another factor to keep in mind when comparing weapons is something commonly referred to as the implicit stat or implicit affix. Right under the weapons ApS, we have a damage stat generally unique to that damage type and this may vary within the same weapon type for certain unique items. Using the example from earlier, although the weapons have the same DpS, we may value [+]Vulnerable Damage% more than we value [+%]Damage to Elites% or vice versa. Thus, either weapon may have a higher damage value to our build with all factors included. It is important to understand that while implicit holds value, this stat is typically in the additive multiplier, and its effectiveness and importance can thus vary depending on the situation.

Skill %

Every ability in the game has something that is known as Skill%. This is generally shown just after the damage range of a skill, let us use Dash as an example. The 36.8% is what we call Skill %. Skill ranks often increase this number, and is increased according to the following formula:

Effects such as X'Fal's Corroded Signet have a flat damage number instead. In season 4, the flat damage number has a hidden multiplier that produces the flat damage value you see on the effect when multiplied by your weapon damage. When calculating the average damage from a Flat Damage source, the damage value you see on the item replaces [Skill%] and [Average Weapon Damage] in the damage formula.

Attack Speed

Attack speed in Diablo 4 makes your character attack faster, and how fast you attack depends on two factors. The first one is Attack Speed% (henceforth AS%) sources from stats, items, paragons, aspects, etc, and the second is the ApS of your weapon. These two are multiplied, and your ApS can be calculated in the following way:

But what are Cap 1 AS% and Cap 2 AS%? Before we go into how Attack Speed affects your damage, we must elaborate on how the AS% functions and what happens when you add different sources. It was discovered that Attack Speed is capped at 200% and it is divided into two individual caps of 100%. For the sake of this guide, we call them “Cap 1” and “Cap 2”. That means that if you have 200% attack speed from Cap 1, you only benefit from 100% of that attack speed. At the end of this section, you can see what Attack Speed sources belong to what cap. Make sure that you check what attack speed sources you have so you do not go over the cap!

So how does ApS affect your damage done? It is a bit complicated, and it is something that you can read in detail in our Attack Speed article. In short, ApS in Diablo 4 has something called breakpoints, which means ApS between two breakpoints has no value until you reach the next breakpoint. Let us use a practical example for this. Puncture has one breakpoint at 1.9056 ApS and another at 2.07 ApS. If you use daggers, any attack speed between 58.8% AS and 72.49% is useless as it does not bring you over 2.07 ApS.

So between 58.8% Attack Speed and 72.5% Attack Speed, you do not benefit from AS%. This means that when optimizing your damage, you want to be aware of these breakpoints to ensure that you do not opt into AS% that is not necessary. In this example, if you were to have 60% AS and add 15% AS, you would go from the 15-frame breakpoint to the 14-frame breakpoint. This would result in a Damage per Second increase of 15 Frames / 14 Frames = 1.0714 = 7.14%. Instead, if you get enough attack speed to go from the 15-frame breakpoint to the 13-frame breakpoint, it would be a Damage per Second increase of 15/13 = 1.1538 = 15.38%. Breakpoints can be found in relevant build guides or the Attack Speed article. Do note that certain skills, such as channeled abilities, do not benefit from Attack Speed in any way.

Tempered Stats

Added in Season 4, tempering is accessible through the Blacksmith and is a system that allows you to put additional affixes on items. These tempered affixes do not have to be explicitly damage stats, but those that affect your damage output are briefly mentioned here. This is, by no means, a complete list and relevant build guides will inform you of what is good for specific builds.

• [+]% Chance for Skill Projectiles to Cast Twice
  This temper is capped at +100% and does not add more projectiles than double at most.
• [+]% Skill Duration.
  In some scenarios, this causes the damage dealt per tick to be reduced (unlike other duration-extending effects in the game). There is no cap as of PTR.
• [+]% Skill Damage
  This temper functions like any [+]Additive stat and is put into the additive multiplier.
• [+]% Skill Attack Speed%
  Most of these belong to the Cap 2 Attack Speed "bucket" with the exception of Wolves Attack Speed which is in the Cap 1 bucket.
• [+]% Skill Critical Chance/Damage
  The stats from this temper function as normal Critical Strike Chance and Critical Strike Damage but do not work for passives such as Precision.
• [+]% Skill Size
  Increases the size of the skill by increasing its radius, resulting in a quadratic growth of the original size. This is capped at 100% increase of the original radius, which results in a 300% increased area of effect size.
• [+]% Damage per Combo Point Spent
  Specific rogue temper, but tempers like this function as standard [+]Additive stats.

Niche cases that deviate from this expectation will be added once verified. In most cases, you can add the tempered stats to the multiplier they belong to. However, certain stats like [+]% Chance for Skill Projectiles to Cast Twice may be difficult to conceptualize. Let us use Rapid Fire as an example and say you have [+]50% Chance for Rapid Fire Projectiles to Cast Twice. Rapid Fire normally shoots 5 arrows, so you would multiply 5 arrows by 150% to get the increased amount of arrows per skill used on average: 5 x 150% = 7.5 arrows on average. This is not added to the damage formula as every skill cannot access this temper, but it effectively functions as a global multiplier to your skill's damage.

Variance

One of the main reasons testing interactions in Diablo 4 proves to be difficult is because of something known as Variance. Variance comes from two different interactions in the game, weapon damage range and skill variance. These two combined cause, up to, a 50% difference between the lowest possible damage instance and the highest possible damage instance. But you may ask, where does the 50% come from? Let us use the Dash ability as an example with its in-game damage range.

We can calculate the average damage of the skill the same way we would calculate the average damage of a weapon. Once we have calculated the average skill damage of the tooltip, we can check the relative difference between the minimum and maximum damage values compared to the average.

Average Skill Damage: (4569+5584)/2 = 5076.5

Minimum Skill Damage: 4569/5076.5 = 0.90002 = 90% of Average Skill Damage

Maximum Skill Damage: 5584/5076.5 = 1.09997 = 110% of Average Skill Damage

This is what we call skill variance. As we can see, the tooltip variance (lowest to highest) is 90% to 110% of the average damage on the tooltip. This exists for most skills and abilities in the game, and most flat damage aspect powers such as X'Fal's Corroded Signet. The exception to this rule is Damage over Time effects, as long as it is not applied by another skill, such as Poison Imbuement, in which case the usual skill variance still applies.

The damage range on our weapons also causes variance in our damage output. If we use a weapon with a damage range of 3269-4903, we can use the same method as above to calculate its variance compared to its average.

Average Weapon Damage: (3269+4903)/2 = 4086 

Minimum Weapon Damage: 3269/4086 = 0.8 = 80% of Average Weapon Damage

Maximum Weapon Damage: 4903/4086 = 1.1995 = 120% of Average Weapon Damage

That means, our weapon damage variance can be as low as 80% of its average damage, to 120% of its average damage. This variance is not used for flat damage aspects, such as X'Fal's Corroded Signet. If we take these two together, it means they compound and we have the following true variance in the game:

Average Damage: see the General Formula
Min Damage: Average Damage x 0.9 x 0.8 = Average Damage x 0.72
Max Damage: Average Damage x 1.1 x 1.2 = Average Damage x 1.32

Enemy Damage Reduction

This damage reduction appears to be the only way the game currently scales enemy damage intake, as it has been confirmed that bosses do not take more or less damage than normal enemies. Usually, bosses appear to take lower damage due to conditional damage increases not applying correctly. Before Season 6, data from levels 1 through 100 was collected and a formula was developed to calculate the visible damage reduction of monsters at any level. The formula was as follows: enemy_level/(enemy_level+39.9933))+0.0256. The new formula has not yet been extracted.

NOTE: Since Season 6, enemy Damage Reduction is consistent across all content, and depends on your level only.