Anyone want to try this? Might be interesting.
Worst combo possible:

You, a beastmaster or some other seldom seen class
Cernd
Haer D'aelis
Amoen
Hmm... tough to think of the other bad characters. Aerie, Imoen, Nalia are probably all not in the "first tier" category. Mazzy might also be included.

Are you say that Imoen, Aerie, Mazzy and Anomen are BAD???!!!

Stop abusing Amoen. He is a fighter and can cast spells ontop of that. Just put the ring of dexterity on him, and he will be pretty good. Replace Anomen with Aerie, who has very low hit points and gain levels very slow. Have the last person Nalia, because she is a thief (a really bad one) and a mage. Here:
1.You, beastmaster
2.Aerie
3.Nalia
4.Haer D'aelis
5.Cernd
6.What about Mazzy?

Now we have a thief (Nalia), two clerics, a mage, a backup cleric/mage (Aerie), a archer/fighter (Mazzy), and a bard. Still, this isn't so bad.

Well, I'm not saying Mazzy, Imoen, Nalia and Aerie are bad, they just aren't the top choices that Edwin, Korgan, Keldorn, Minsc or Viconia are.
Imoen might be the worst of the lot since she is always trailing in exp by large amounts. Nalia's not really bad but her thieving skills are definitely lacking. She's like a brawnier Imoen. Aerie is fairly decent if you can keep her out of trouble, though I would still take her before Amoen. Mazzy has a 15 strength, and that's pretty bad. She's a good archer, but then so is anyone with a mere two proficiencies in short bow.