It took me about 10 tries my first time just to down him on normal, though I am still in mostly questing blues, the problem was that the adds spawned too quickly for me to kill them if I wanted to position myself out of the ice and then make sure the healer didn't get aggro. I was spending too much time running around trying to survive.

I downed him by doing as others have said and camping out in the final room after gathering harpoons on a pull that I reset. Have one character start the encounter and then AOE tank like 20 mobs at once, blow your shield cooldown and AOE them down like mad, spam your biggest heal. Once those are dead, run the other toon back while trying to still hit some DPS and heal keys to keep the others going while you're running. Once you're all in the room, blow some DPS cooldowns and get everything under total control. Once you have everything going smoothly, just kill whatever spawns, and no worries about the ice. Run out and shoot him when you get a chance. Once he lands, it's tank and spank EZmode.