I think it should be doable like all the other dungeons with heroes +hench or 2guys with 6 heroes.
So far i tried a few skills
judges insight: sounds nice but almost useless because I'm always blinded
wards: might be a good way to deal with all the earth damage that usually whipes your party. I would use ward against harm + elemental + stability and maybe some paragon shouts like stand your ground. But the armor bonus doesnt stack beyond +25 according to wiki so im not sure it makes sense to have more than one or two wards at a time.
ray of judgment: i think a group of about 4 smiters with ray of judgment should be able to kill the undead very fast, but would a hero team use that skill instantly before the enemy group can scatter? And for all non dead enemies a smiter group would have problems because of low armor and damage output.
light of deldrimor: a real killer

so far im playing a warrior with 2 knockdowns (signet of judgment and brawling headbutt ) in combination with holy strike and stonesoul strike. This works pretty good.
Anyone else who has completed this dungeon with mostly heroes? Any good ideas how to survive the undead groups.