I know that trap. Left from the main chamber is a hallway that leads to a floor sarcophagus. That trap is detectable with a high enough skill, but I've never had the skill to disarm it (even with a pure Dwarf thief. I think it's a scripted trap, and then you have all those skeletons that pop out. And elf character might be able to resist it (I know they didn't implement elf and half-elf sleep resists in BG, not sure about IWD) but usually, I send a sucker in to set it off then my cleric rushes in turning undead with a heavy on a flail to bash the skeletons to save them.
I also hate imbued wights. You can really only counter their MMs with a shielded mage or bard, but then you're putting a squishy out front with potential skeleton archers and (in that fight) a skeletal mage. Usually, after I have an invisible thief scout forward for traps, I stay near the entrance and try to lure in or wait for wandering skeletons. This lets me pick off the chaff without alerting the heavies. Then, my ranged characters pick off that skeletal mage behind the post without alerting the wights. Then I can send a shielded mage forward to alert the wights. I think it's the room after that that's really nasty. You're just dumped right in front of a ton of undead. I'm turning from the start there to keep their numbers down and slowly working my way through.
I think it was clever that the devs made the first dungeon stretch all low-level undead. This way, they can have mobs and mobs of monsters like in the rest of the game, but a cleric with turn undead can keep it manageable.
Was this a no reload run? If so, that's too bad. This seemed like a pretty sweet party setup. Are you thinking of a next run? If so, with what?