As I recall from doing it, most of his damage comes from aoe ground effects and meleeing, so as a Commando, I blew all my dps cooldowns while Vikk tanked him, and when Vikk went down I kited him around the area, using DoTs, instants, and the occasional channeled cast when I had time to plant my feet. I believe you fight him on a curved catwalk area, with plenty of room to run from one end to the other, then use stuns/knockbacks to get past him when you have to turn around.