Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

Buffed it has a 51 ac, 600 Hps, and a 50 percent miss rate. One buffed fire giant I can use to solo the whole stage. If I add a vamp, it makes it even easier. Plus you're not worried if the balor drops your summons in 10 rounds or so, the damage they do will replace a lot of GMMS you'd have to send in anyway. The Balor is not that tough by himself and he wont be able to drop your fully buffed summons as quick as you think.

Whats the fortitude like? If he fails the vamp feast, he is gone. I have done that with the other bosses, sometimes only succeding on a roll of a 1. Some spells lower the saves, like energy drain. Cloudkill is great at it too, but daemons often have poison immunity. If you can lower the saves first, you might have a "gamblers chance".

He is immune to ability drain so I suspect you can't lower his saves easily (not through energy drain/enervation anyway).

Fortitude is 45+, immune to negative level, and got epic resilience.

Correct, he's basicaly a stronger version of the pit fiend or the Yuan ti queen when planning out a strategy. Pin them, and blast and/or use summons to take them down. Force spells work well, I imagine cold spells work a bit better. If you have wail you can drop most the group with one spell at level 30 and a descent ability score (int). I just like dominating one because the buffed giant can last awhile against him and you can even call your other summon back if it starts to get too injured and allow it to regen while the dominated giant takes the brunt of the damage before sending your summon back in. Even with no focus in evocation, you should be able to pin him with a bigby at level 30. If you have reserve feats like invisible needle, you can spam those and conserve your other spells untill you believe you can finish him with a flurry of spammed spells.