So I've been talking with some kingslayer buddies of mine. They suggest, since spirits seem to kill some of us a bunch, that we try a position similar to the following masterpiece:
Not drawn to scale. Also: Runnings-away do not have to be at the opposite damned side of the platform. I just had a limited circle 
Basically, if we put Hep just a few yards (more than five) in front of the everyone-not-tanking, he'll soak any of the spirits that happen to get through the AoE spam. The idea is to run out as a group when the Lich King starts summoning (or right before, if we have a timer for it.) That nerfs us Melee folk a bit, but if it keeps us all alive, I think it's worth it. It should only require a few seconds of movement-downtime. Thoughts?