Drop arcane blast at the end. Four arcane barrage and arcane missles. Odds are like 90+% you will have proc'd missle barrage each rotation.

Glyphy holy nova on your priest, keep three mages within range of holy nova, keep prayer of mending up and spam holy nova as needed. Your dps will make short work of this boss once you get a rhythm.

I will admit the presence of my shaman makes this trivial now with NR totem and healing stream.

Also, I've learned that taking the transitions slow to ensure you have good aggro on your tank is key.