This is all depending on what abilities and spells will be available. But inspired by how my BG2 team usually ends up.
A) Wizard, Tank
B) Fighter, Damage
C) Barbarian, Damage
D) Rogue, Damage
E) Priest, Heal Support, Semi Tank
F) Chanter, Support, Damage Wannabie
F) Wizard, Damage
(F can be different depending on what you think you need or what kind of party members you like)
[F] A - C - _
[F] B - F - E
[F] _ - D - _
Fighter at front to take a few hits while Wizard casts tank spells (if not pre-casting).
Wizard is un-kill-able for a little while, so the team unloads while tank spells are active.