It took us basically a full night before we killed him, same issues you're describing. We had 3 shamans, 2 resto and 1 enhance keeping tremor down in the melee group. We had everyone spread out in a semicircle behind him, 3 decursers spread out within that semicircle and a resto druid standing well behind everyone to help decurse/heal those that got airbursted.
Airburst is a 1.5s cast and you have a second or so after the cast before they're out of range, if someone gets hit with that and they still have grip then the decursing really was too slow. If someone gets grip right before a fear and it doesn't get cleansed quickly they probably need to trinket out of it to help the decursers get to them, but once again you've got a gcd or so from when grip is cast to the earliest you can be feared. If someone doesn't have their trinket up, they need to make sure to get much further from the fire than they normally would, even if it means running out of dps range briefly. Almost every death is in some way your own fault.
We had alot more of our wipes from fall damage, or people dying because they got grip right after the airburst and didn't use healthstones/pots to help buy time to get themselves back in range. Even on our kill we had someone die at 22% or so, and the MT died at 12%. Made for quite an exciting final phase with only 14 people left alive
