I like to spread out, bind a single movement key to each of your chars (I use forward). So that way you can move just a single guy at the time. Nuke him down and move you tank away when he starts beaming out shadowbolts all over the place for the win. But I have 4x Shaman which make it ez with grounding totems as it eats the deathcoil. To be honest this guy is the hardest part of the instance on Normal, by far.