I've been banging my head against this one too. But we're still carrying some dead weight who get hit by Blistering Cold and can't los the frost bombs because they have the reaction time of a tree sloth.
It helps a lot if you have healers use a timer for magic buffet, its an 8 sec debuff that is refreshed when it reaches 2 seconds, so you only need to LOS at the 2 second mark in order to drop your stack. Also having 1 pally standing out and healing themselves + the tank helps, they can bubble if they get frost tombed. As for getting hit with blistering cold nothing is gonna help you there.