Diablo III - Mechanics

[Dr Super Good]

Statistics

Primary Attributes

All primary attributes improve your ability to take damage. Each class has a primary attribute that improves damage. Primary attributes are mostly gained from auto allocation when gaining levels and from Gear.

Strength

Each point adds to Armor.
Primary attribute of the Barbarian class.​

Dexterity

Each point increases Evasion from Dexterity based on a bracket system.

0 <= Dexterity <= 100 : Evasion = Dexterity * 0.10%
100 <= Dexterity <= 500 : Evasion = Dexterity * 0.025% + 7.5%
500 <= Dexterity <= 1000 : Evasion = Dexterity * 0.02% + 10%
1000 <= Dexterity : Evasion = Dexterity * 0.01% + 20%
​

Primary attribute of the Monk class.
Primary attribute of the Demon Hunter class.​

Intelligence

Each point adds 0.1 to all Resistances.
Primary attribute of the Wizard class.
Primary attribute of the Witch Doctor class.​

Vitality

Each point adds 10 to Maximum Life.​

Primary Attribute of Classes

Each point in the primary attribute of a class boosts damage by 1% of base weapon damage in addition to the normal attribute effect. It is desirable to mass such attributes to take advantage of the double effect.​

​

Defensive Attributes

There are various defensive attributes which affect how durable your character is. The best defensive attribute for a class is usually boosted by the primary attribute for the class. Defensive attributes are mostly gained from gear and primary attributes.

Armor

Armor reliably reduces the damage taken from all damage sources by a percentage. Higher Armor scores provide larger damage reduction. Higher level damage sources will reduce the damage reduction from Armor. Armor is mostly gained from gear and the Strength primary attribute.

The formula for damage reduction from Armor:

Level = Level of damage source
Armor = Armor score of damage target
Reduction = Percentage damage reduced.
Taken = Percentage damage taken.

Reduction = 100% * ( Armor / ( Armor + ( 50 * Level ) ) )
Taken = 100% * ( ( 50 * Level ) / ( Armor + ( 50 * Level ) ) )

Against a level 60 monster you will need 3000 Armor to reduce damage to or by 50%. Monsters in Inferno difficulty have levels above 60.​

It is currently unknown if damage target level plays any role in improving damage reduction from Armor. It is only known that the listed damage reduction from the character statistics window is shown for a damage source the same level as the character.​

Evasion

Evasion is the chance that incoming damage sources cause 0 damage. It is the result of many Evasion sources rolling independently in parallel. A damage source will fail if any Evasion roll passes. More and larger Evasion sources result in a higher Evasion chance. The mechanics of the Evasion rolls prevent a 100% Evasion chance. Evasion chance does improve durability on average but is unreliable so not suitable for low health situations. Evasion is mostly gained from skills and the Dexterity primary attribute.

The formula to calculate Evasion chance from many Evasion sources:

Source = An array of Evasion source chances.
n = Number of Evasion sources.
Evasion = Resulting Evasion chance.

Evasion = 1 - ( 1 - Source[0] ) * ( 1 - Source[1] ) * . . . * ( 1 - Source[n-1] )

when n = 2
Evasion = Source[0] + Source[1] - ( Source[0] * Source[1] )

Having 2 Evasion sources of 15% each will give you a 27.75% Evasion chance.​

Resistances

Resistances behave exactly like armor units except the unit scale is 0.1 and only affects a specific type of damage.​

 

[Edhel-dur]

I like how each primary attribute gives some form of defense.

 

[Dr Super Good]

What is even better is that all resistances means all resistances. It will boost everything from Arcane to Physical resistance.

You can also evade magical attacks.

 

[Edhel-dur]

So than what's the difference between Armor and Physical Resistances?

 

[Dr Super Good]

Physical Resistance only reduces Physical damage by a percentage based on the level of the damage source and how many points of it you have. Armor reduces all damage types by a percentage based on the level of the damage source and how many points of it you have. The points in Physical Resistance are more effective than those in Armor but are much more difficult to obtain.

They stack as well. If you reduce damage by 50% from Armor and the particular damage type by 50% from resistances you will reduce that damage type by 75%.

Resistances are worth more than Armor when it comes to reducing damage but are specific. If you get a piece of gear that improves physical resistance by 100-200 points you will take very little damage from physical attacks compared to before. To get a similar reduction from Armor you will need 1000-2000 Armor.

Be aware that Diablo III has a lot of damage types and most enemies deal damage other than physical.

You can think of Defensive Attributes as being 3 tiers.
First you have Evasion which has a chance to negate some attacks completely.
Then you have Armor from your Gear and Strength which will reduce all damage you take.
Finally you have Resistances which will further reduce the damage based on the element type.

All classes will have similar Armor levels. The Barbarian will have the most Armor due to high Strength but the quantity more is probably not even double.

Resistance as much rarer to come by with only the Wizard and Witch Doctor being garunteed to have them in large quantities from their Intelligence. Most points of resistance will have to come from Magical, Rare or Legendary gear with a modifier that adds points directly to resistances.

There is a passive skill for the Monk which makes all Resistances equal to your highest resistance. If you stack gear for a specific elemental Resistance on a Monk you can really take advantage of this skill and have stupidly high values of Resistance.

Both the Monk and Barbarian are melee classes so have a 30% damage reduction from all sources before applying any extra damage reductions.

 

[Edhel-dur]

Then you have Armor from your Gear and Strength which will reduce all damage you take.

Does that mean Armor reduces other types of damage besides Physical?

 

[Dr Super Good]

Armor reliably reduces the damage taken from all damage sources by a percentage.

What gave you the idea it would reduce just physical? It is the common damage reduction for all classes.

 

[Edhel-dur]

I just forgot some basic mechanics of Diablo I guess. Too much Wow.

 

[Dr Super Good]

I just forgot some basic mechanics of Diablo I guess. Too much Wow.

It is new to Diablo III. In Diablo I and II Armor reduced the chance for an enemy to land a physical attack on you.