Three mechanics:
- move out of the fire;
- dispel-leaving-a-puddle;
- ray of death (essentially, Heigan dance).
In that order.
- Move out of the fire. There's a mark on the floor so nobody should be hit with the meteor itself, and there are arrows on that mark showing direction in which fire will spread.
- Dispel at the right time. Tunnel-visioned healer sees different color in his Grid, automatically clicks it, bam! there's a puddle on the floor. And pray that it is a puddle of fire, not remains of some unfortunate melee.
- If you're a melee, tank should be dragging Halion around so nor him neither you should even come close to the Cutter. If you're ranged, look! Ideally, you should be right behind the orb when the Cutter activates. That way you can reapply DoTs, HoTs, buffs and debuffs before you absolutely have to move.
Okay, if you stay really close to the orb ahead of you, you don't have to move in normal mode. But come on, we all know we want heroic. Two rays of death for a price of one, only in Ruby Sanctum.
They say that in heroic-25 each meteor spawns adds and, more importantly, zones that appear on the ground affect both realms — so dispelling everything on sight is much more worse than in normal. I've yet to read or see something on 10 heroic.