[daan]

NPC's that might help you :
Keldorn : Paladin, one of the best tanks in the game, when equiped with dexterity boosting items.
Edwin : THE best mage of SoA, only a self-played sorcerer would match his power

I myself would go for the mage though, you seem to be lacking there ..

Mazzy = good fighter + great archer 1.0 fighter
Minsc = good fighter 1.0 fighter
jaheira = good druid / backup fighter, potential tank with 0.5
champion's strenght and Harm 0.5 fighter / 1.0 healer
aerie = medoicre healer/mage 0.5 mage / 0.5 healer
you = fighter 1.0 fighter

So you got 3.5 fighters, 1.5 clerics and 0.5 mages

Mages are quit important, and Edwin is the best mage around.
He IS evil however, and WILL fight with Minsc, but you can deal without Minsc very easily, since keldorn is a much better fighter.
I'd say, dump aerie and put in the real mage, dump Minsc and put in keldorn ...
Keldorn sometimes has problems with Edwin, he never fought in my game though, if things get hot, just kick Edwin out, and get him in the party again after a while, he should be fine then.

Hope this helps