The best way to tank this boss is to pull him into the stairwell that the players start in and gets blocked off. Have the tank put his back against the barrier in the corner and tank him there. Then pull the add to the center of the bottom of the stairs. This effectively keeps the seacaps to migrate to the add and you don't have to kite him all around the room in the hopes of picking of the seacaps. Then when the second add pops out, dps the first add down right there at the bottom of the center of the stairwell. Rinse and repeat.