http://www.notacult.com/episode3.htm
This page shows you a lot on mitigation on live.
Notice the damage he getting on the paladin using an 8 dmg weapon (notice the first screen has 'your engulfing darkness spell as worn off' message thus using a serrated bone dirk). He pierces for a max of 11. This is with full shaman buffs (hes grouped with Blart).
Now scroll through the other screens and you can see that against casters he is piercing a lot harder. He is doing upwards of 35 dmg to the clothies. He also does decent dmg against a cleric. I guess the cleric has his class quest armor, which is going to be far inferior to the paladin's planar no-drop stuff AC-wise, since it's not purple and they loot a froggy crown.
I know these aren't logs of 100+ hits, but I think it is still definitive enough to get the idea that AC played a larger part in PVP melee than we are seeing currently on red99.