As far as I knew AC did only effect mitigation, but if the damage was reduced to 0 it would count as a miss. So the way combat worked is as follows
- Attacker rolls to hit
Defender rolls for dodge, parry, riposte, block and what not.
Attacker rolls for damage
Damage mitigation is applied
If the damage is 0 or less it counts as a miss
If the damage is 1 or greater it counts as a hit.
Like I said this is just what I read on boards and such