My favorite party (the only one I completed all the way through SoA AND ToB with) was:
My main character, Dalen (Chaotic Good Male Human Berserker dualed to Thief)
Anomen (Fighter/Cleric)
Minsc (Ranger)
Nalia (Primary Mage)
Imoen (Second Mage, about as powerful as Nalia by the end of SoA and definitely so on into ToB)
Aerie (Backup Cleric and Mage, and very powerful into ToB as well.)
It was the best blend for me; my own character was both a Tank and a Thief, and then with Minsc and Anomen, I had two additional powerful tanks. Anomen and Aerie had the cleric spells, and I was definitely mage-heavy with three magic users (Nalia, Imoen, and Aerie). Minsc's ranger spells also came in handy in a pinch later on. Also: everyone in the party was of Good alignment, so no b*tching about high rep points.
With this party, I rarely had to reload a battle, and actually won the endgame without a reload (for SoA, that is.
)
-Sazerac