I always solo'd this as arcane or fire at 85, due to the fact that I would have MC problems as frost. Not sure if they've fixed it, but you can run out of the room right after starting the encounter, and run to the beginning of the instance. Then, you can kill the four advisors one by one at separate spots in the raid as you slowly work your way back to kael's room. That way, once phase 3 comes, you only have to fight one advisor at a time again!
Here's an old video of me doing this as arcane in Cata:
It's a boring video, but you can see how I managed the adds at 85. I do indeed use the staff to protect me from disorients and remote toy stuns, but I make sure I swap to my real DPS weapon for nuking. A lot's changed since cata talent trees, but you can more-or-less follow the same strategy.