I've done this instance 4 times now and in 3 out of those 4 the final boss bugged, making the quest stall so the only solution is to start over. I'm getting frustrated because I can't complete this instance on my hunter.

The problem seems to be that if I kill the boss too fast, before he's had a chance to go through his three phases, then he just dies and the quest won't advance. If I try to keep him alive, then he has time to throw around all his death squares and debuffs and I end up dying. I'm not sure how to complete this instance. I'm basically doing small attacks until he does his reflect, then I remove it and kill the adds. By the time the second group of adds appears he's already dangerously low on health (I have to turn away because my auto attacks are hurting him too much.) In the meantime though, he's casting something that's draining my health (skull icon I think) and I end up running out of healing/defense skills/pots and next thing I know I'm dead. I'm running out of the red squares every time I see one but it's not enough. My health drops too fast. If I start using high DPS skills he just doesn't make it to phase three.