Greetings.
I'm going to go mad, I think. I've tried this achievement 3 separate times now with several different strategies. (Hunter pet strat included) I've put in multiple tickets to Blizzard. This thing has been bugged for ages. A friend of mine randomly got it when he tried in on HC 10. I just tried it and nope. Even with 8 people in the group, 3 people channeling, healing up with 10s left and coming out, going back in, trying the spam click method. Nothing works.
Does anyone have some sort of super fix for this?