First facts:
The key to win this fight is bringing a decent amount of AE/ AOE damage with you. About 250k+ should be fine, not reaching 200k raid dps.... don't even try this fight.
The mob might be pulled from the edge with a Templar's hammer or similar. We fought the mob on the path where the Syfak encounter starts.
At 94% the mob spawns 5-6 2up heroic adds periodically, while he gets immune to damage and casts a reflect cloak on himself. I suggest a zerker or a SK to deal with the adds (because of the AOE damage).
1) There is a red writing on the screen, when the cloak is setup on the mob. Similar to Syfak the cloak must be removed by a healer class. Pay attention to the cloak or it will kill yourself or a part of your raid fellas. No single target damage on main mob during cloak phase!
2) You must kill all heroic^^ adds real fast, if you fail, the surviving add will change in an heroic^^^. If you fail again it grows in an epic x2, than x3. So not killing all heroic^^ will usually result in raidwipe.
Deal with the three successive AOE's properly and have enough AOE DPS for the adds will make this fight fairly simple.
The adds are doing nothing special with the right amount of dps.
Gz on two Tier2 gloves.