Artic Troll (melee) : 33 AB
Mastiff (melee, sneak attack, KD) : 33 AB and coming out from stealth
Ice Ooze : high AB, RTA cold attack with DC 37 dealing 100 damage if you fail the save
Avalancher (huge spider, melee) : 33 AB, comes out from stealth with a paralyzing attack and has 25 DR
Artic spiriter troll : a bunch of epic spells, hellball, epic gate, vamp feast (and I think entropic husk too)
I suggest to lower the AB of all mobs by at least 4, to lower the DC on the RTA to 30 at least (which is already seriously high, I understand it was probably done to damage the evasion builds but think about the others) and the most important point : tweak the spellcaster seriously because he's crazy hard alone and can come with 3 trolls spamming knockdown on you.
As it is now it's too challenging, it requires powerbuilding and/or optimizing, which is not a good thing. I've yet to go there in a group but I imagine the spawns become more numerous and it can be rather nasty if a spellcaster is left unchecked