[SixOfSpades]

I can speak from experience that the combo of Imoen + Valygar is a quite effective one: Valygar creeps along in Stealth, while Imoen stays a few paces behind him, checking for Traps. If he spots a bad guys, she's still out of sight, and if she spots a trap, they both halt until it's dealt with. Imoen + Jan provides similar versatility (and, given a good STR item, just as much Backstabbing fun), but since your PC is already half a Mage, you don't need another arcane spellcaster. On the same note, Gnick makes Aerie, Anomen and Viconia almost completely superfluous.

It seems to me that with Korgan as the main Tank, you'd have Jaheira, Keldorn and Valygar as backup Tanks, and Gnick and Imoen in the back. Seems very solid to me. I should also note that in the talk about Valygar I've seen recently, nobody has yet mentioned how extremely spiffy his armor is. Who cares if it's leather, it's better than most of the Plates out there. He makes a darn good meat-shield, trust me.