First, your choice of companions needs to be revised. Elanee is great ... absolutely bring her; but the Construct should not be there. Khelgar is good, Brother KI is good*. Casavir is good. Even Grobnar is pretty good depending on what spells he learned, but the Construct is a liability for a reason that is about to become obvious.
Second, and this is critical, everybody needs to be regenerating. You should have enough Rings of Regeneration/Power to go around. There is one character who can't use them, though - need I say more?
The third consideration is spell selection, especially for Elanee and Zhjaeve (you say your PC is a caster, but that's not very specific). E & Z's offensive spells are of little use here (except Acid Storm), plus you have unlimited firepower from AJ, so concentrate on buffs, heals, restores, summonses, etc. There is one critical spell for Elanee to have memorized - without giving away too much, think of your last couple of confrontations with Shadow Reavers and ponder whether you might not be meeting more of them. Plus, one of Zhjaeve's possible spells is THE best spell in the game at this point - both defensively and offensively - and you should have at least a couple memorized and saved for the right moments. And of course, you need everybody immune to fear somehow.
And as has been said before - don't rely on resting much. I hope you have some long-lasting buffs you can cast, and be prepared to swallow your pride and plink away with a crossbow for a while.
* "Brother KI? Who the hell is Brother KI?" you say? See metatheurgist's post above.
[edit] I said Grobnar could be good - but probably not for you since you're a caster; you need a meat shield.