Heyo! Our guild also had problems with the frost phase. I assume the frost patches on the ground are screwing you over? Us, too. Until we found out that you can dispel the debuff within the bubble and it won't leave a frost patch on the ground.
We have everyone together in one group running around the inside of the circle. Assign one healer to dispels and the other healers to heal any damage that might come about in that phase. Anyone who gets the Frostflake debuff on them will dip into the bubble and wait for the healer to dispel the debuff (which should be nearly immediately as they enter the circle) and then they can run back out and continue dpsing/running. Just repeat this throughout the phase and you'll be golden.
Your healers can put the Frostflake debuff and the water bubble debuff (forget the name) on their raid frames so they can dispel as early as possible to minimize damage and so people don't fall too far behind.
Have one hunter use Aspect of the Pack. There will be no knockback from the magical damage and it makes that phase a joke using that dispel method. Your new worry will be running into the wall rather than the wall catching up to you.
In regards to the "legitfulness" of that dispelling strat, I think a few people have asked Blizz about whether it's a bug or intended. It's been a while, but I think Blizz either never said anything about it, or said it was intended. So if you're touchy about that, no need to worry.