Another Papi post on how armor affects PVP damage (Posted: Wed Feb 06, 2013 12:14 am).
[quote="Papi"]Each time you hit the game uses a random number generator to pick a value between your max and half your max. So your average damage will be 75% of your listed max and your Minimum damage will be half your Max damage. Of course this is only against a mob with zero armor.
Min damage = 50% of max
The % damage you opponent will take is 400/(400+100) or 80% of the random damage you do.
Since you will average 75% or 300 per swing, the average damage your opponent will take is 240.
This formula fits very nicely over the data points taken.
Not included is how your damage is effected by the level of the mob. That is next.