You cant ignore the right side portal, as the boss goes immune. To be honest I just took my shaman in there and blew his ass up. Its like 100k? hp's or something, and hits weak.

Overall I spread out best as possible, healed through the void zones, and took shaman only into the portal. I had to make a different follow key that was for my DPS only. This is how I got it.

To be honest, I had a harder time with that one mob -- then I did with the rest of the instance.