I just cleared the Frozen Peak quest (that Crusader one) and oh wow it's awesome. I used to hate frostbites (and I might re-hate it at later point) but it was really, really smart. I thought it would be too difficult (Miser + Hoader + Parched plus alpha at the same time?)
Before this dungeon, the default solution to any difficult dungeon was stacking resistances. If you can stack your resistance around 50% you score an easy win. But this dungeon is very different - it makes damage reduction much favorable over resistance, which basically means Platemail over Dragon Shield. I felt like I was playing a Vampire which is my favorite monster class, and because of this I really enjoy the mechanic. Also the optimization of caring about the frostbite was delightful to do.
However I can't imagine how this dungeon will transform into a frozen nightmare when I don't have platemail. (I actually hadn't noticed that 0 damage will remove the debuff while playing Extreme North.) I also tried to get enough damage reduction to auto-win the boss but it was super difficult and required a plenty of scumming.
Another quest there was done by acid caster approach so that I didn't had to kill anybody (but petrify them). But hey, did you intentionally make a caster build awful there? Evading nasty debuffs by fireball or knockback had been a good idea. But here, the boss is quite tanky plus magic resistances plus that monsters lying around blabla so that it makes caster approach much less attractive over standard hybrid. If you did so, I think it was a good design approach.
By the way, how about giving some god boons with new traits? For example, Cleansing removing one stack of frostbite, or Chaos Avatar removing 20% of protective blessing.