Facts about defense
Does not reduce damage directly
Many of us know this. This is one of the "missing" features about defense in Diablo. No matter how much defense you have, when a monster hits you you will take the same damage.
Defense when running
While it's commonly said that defense = zero when running, this is not true. You are much more likely to be hit while running, but the actual game mechanism is that the entire to/hit formula is ignored, and that any attack that can hit will will deal damage.
The difference is that by ignoring the to/hit calculation, factors besides defense, such as Clvl and Mlvl, are ignored. Thus low level monsters that would often miss a naked high level character who was standing still, will usually hit that same character, if they are running (even if they have on heavy armor).
To benefit from defense you must walk, stand, or attack.
What Defense does
If you hover your mouse over the defense rating number you can see that chance as a %. This is being recalculated every time you hit a monster or a monster hits you. So if you want to see the % a zombie will hit you, just go and hit one, and the game will calculate it.
- Some physical attacks are of the Ignore Target's Defense type (such as Smite and guided arrow), defense does not help against them.
Defense and special damage
Defense has no effect on elemental, poison, or magical attacks.
However if Skeleton archers shoot fire arrows at you, and the defense blocks the arrow, then you will not receive any fire damage.