Got him to about 4% on my Frosty but ran into several problems (other than cloth armor): he is immune to Frost Nova, which was an ugly surprise. I couldn't get Frostjaw or Time Warp to work either, so you'll be short a bunch of tools in the fight. The real problem, oddly enough, was that you're accompanied during this series of quests by a mage named Magister Serena, who fights alongside you and actually does some pretty decent damage. I was counting on Serena but she vanished after about 10 seconds into the fight.
I don't know if this is a glitch or a dig in the ribs from Irvine, but I would have won the fight easily with Serena on the job.
So maybe ask Serena if she is ready before the fight? Otherwise, make sure you invite your Garrison Team to hold aggro.
Just as an added amusement, the "nearest" graveyard you get sent to is in Tibet, so it will take you the better part of a week to get back to your body, but of course you can't rez at the Spirit Healer because you'll get Rez Sickness. You'll love the trip back. Bring several books along; maybe The Brothers Karamazov, and stay away from those yaks.