Vaan, actually, is currently carrying a polearm, it's called a spear but I've never seen a spear with a rectangular head. He's still the main character, has plenty of health, and the heaviest armors I've found so far. He also has a decent power over weaker white and black magics, so he's a backup healer as well.
Basch has a sword and shield, a tank's worth of health, and currently no great magical power.
Fran is, essentially, my red mage, though she currently has a better ranged attack than Balthier. She has the basic white, black, and green magics, branching a bit more heavily into white. Main healer.
Balthier is a bit of a loose end at the moment. I don't want to make him a close-ranger, but his shot is still comparatively weak. He's got decent health, and could be considered a backup backup healer.
Ashe I haven't done a lot with yet, but she's a sword & shielder with large health and a good use of white and black magic, more heavily on the black. I'll see how she does in close combat, and if I don't like it I'll probably be converting her to a full-on black mage.
I have done literally nothing with Penelo yet, as I just got her back and didn't use her on
Spoiler:
Judge Ghis.