This is all sounding incredibly un-killable...None of quarm's AOE are resistible, and they power up as he loses head apparently (we're guessing right now). The lowest form of his Stun AOE in the database is a 6 seconds unresistible stun, which, since this version of quarm is also flagged unslowable, is pretty much a game killer. None of the walls blocked any of the AOEs. None of the debuffs had any curable counters.
I think your only hope is to get Hobart to update the potime zonefiles