I've been doing testing against belial on inferno, and I'm pretty sure the 100% absorption cap is after armor/resist mitigation. Probably after mitigation from stuff like blur too. I have 60% damage reduction from armor, and another ~40% from resists for a total of 76% damage reduction (depending on type, but roughly). Belial hits me for 60k without force armor, but with force armor and 38k health, I survive a hit. There's no way I could survive a hit if the absorb was calculated before damage reduction, because that 60k hit would be something like 250k.