#0 - April 17, 2009, 3:56 a.m.
1) It drops without absorbing attacks if the mob hits you between your crit and SD going up.
You crit
Mob hits
SD up
SD down
2) It absorbs multiple attacks if they are near simultaneous.
In multiple mob situations, it's possible they could cancel each other out, at least over time. Without looking through every single combat parse, it's impossible to say. It's going to be encounter specific.
In a single mob encounter, it means that SD is not providing the level of mitigation it should. And the first bug listed definitely happens against single mobs.
I just finished tanking H UK and checked my combat log for Ingvar. I have at least 2 places where I crit (with Maul, Mangle, or Lacerate), Ingvar hit me (no absorption), and savage defense went up and then faded on the next line in the same second.