We (In Excelsis, Laughing Skull) killed him a few nights ago after bringing him down to 1% the night before.
You have two different approaches to it. You either give yourself 3 minutes to kill him, or you prepare yourself for a Sons fight, survive that, then kill him in Phase 3.
The only problem with the latter approach is the randomness of it. Our first tactics/attempts brought balanced groups to the fight, and we tried to fight him like Onyxia, with 3 different phases and tactics. We got it down to 35-40% in p1, tried to survive and kill the Sons, only to see half the raid wipe in a 3 second timeframe to 2 random lava splashes. Any fight in p3 is too dependant on sheer luck, imho.
So basically, we loaded up on rogues (we had 12) like everyone else, had limited priests (5, I think) devoted to healing the MT, and a few paladins/druids to heal the DPS. Presto, dead in 2:55.
Hopefully, the patch will allow more balanced groups to beat him.