Originally Posted by
Coal
You can continue dpsing the boss during the kite phases. Just trail behind him at max melee range. If you get too close, even from behind, he can still Chomp you. Use Death's Advance when the boss speeds up, then stay safe when you can no longer keep up. Just strike him a few times or death coil as he is passing by at high speed. As unholy, you might want to use Festering a lot in the stack phases so your diseases keep ticking during the kite phases. I would save cooldowns like gargoyle and unholy frenzy for the stack phases. When bats come out, use gorefiend's grasp to group them up quickly since they seem to be immune to remorseless winter. Use your CDs and second potion on those bats to help your raid get them down quickly and boost your own dps in the process. And don't forget to AMS. A lot. Tons of magic damage going out throughout the fight so get some runic power and increase survivability. As frost, I also use outbreak on the jailer while I'm still dpsing the boss and then switch to the jailer when I can't keep up with boss.