Not sure if it helps much, or if you're doin it. I have a similar spec to you and keep Seal of Command up at all times while fighting mobs, then switch to Seal of Vengeance for boss fights. So far I've only been tanking heroics on that part with my main tryin to gear up a bit more to try and multibox them, but when I run that part, I tag the first bad guy I see pops up there and the SoC tags them all right off the bat. Couple things that might help. Watch your taunts and space them out along the phases. Use your totem on your shaman that slows the enemy's movement, see if that'll help any. Maybe even the one that taunts enemies onto it, spread those out too to help with phases 3-5. But if you keep them at the top of the steps right before you go into the room backed up to that circular part, they should be out of reach of the laser.