Really is a fun boss to fight, when I did it the first time (78 to 79) with my DK's, I would kill him just after his second wave. But now on Heroics (few toons with 540 defense and one being 23000+ HP and the rest only about 20 to 21000HP) I have my 20 min CD Army of the dead which I save for him, and on normal I get him down to 30% or lower before he even gets his first wave, on Heroic, I get him down to 60 to 50% before he does his first wave.