A couple of things after having finally killed this boss on heroic mode. Deaths must be avoided as much as possible, hybrid classes that can heal themselves should be doing so during the 2nd phase like Moonkin druids, Ret Paladins and Shadow Priests who have some form of heals available for use. Health stones and any other items you can use to keep your raid alive like a Lightwell or two will make things go a lot smoother. Healer deaths = instant wipe and people not properly controlling the Unchained Magic will kill your raid quite quickly as I have experienced. Next to Professor Putricide, this is the hardest heroic mode encounter from both a healing, DPS and raid coordination perspective. Every mistake can make a difference and a couple of little screw ups can wipe the raid.