Deaked into ICC with a donor-geared char who wasn't faction-maxed to clear entrance trash... Lo and behold, I got squished a few times by mobs with over 300k hp (the big skeletons had something like 1.3 G hp!!!). I had everything set at 10-man normal, DGA buff up, the works and I could barely hold my own. Tried with another char on another account with the same set-up and the result was the same. Funny thing is when i killed a mob, it's hp came back to normal (see screen shots below).