Tir McDohl (Suikos) (4) - Lategame insane damage, earlygame ST ID, midgame MT ID, fast, and...
Riou (S2) (3) - ...With this guy, Physical MT ITE damage (at least I think it's ITE). Also an emergency healer, along with being fast and evasive.
Lilka (WA2) (2) - Buffing and magic damage. Magic damage isn't MT until later, but eh. Also emergency healer and revive specialist. Also, literally never runs out of resources once you let her get going.
Lucia (SH2) (1) - ...Despite sucking in a duel, she's actually not too bad in a team setting. Her Aromatherapy skill is actually pretty interesting, and she can kind of attend to her defense problem with her own spells. Another plus for her is helping Tir and Riou be more awesome later, and Lilka around mid-game, I think... Ricardo would've been better, but I only had 1 point left.
Mint (ToP) (Free) - Unlimited healing. Lilka and Riou are there to panic heal if Mint goes down, but pretty much doesn't ever stop healing.
Biggest weakness: Status resistance. Lucia is basically the only one that can get it, and she can spread it around (for sacrificing other useful ATK or DEF buffs), but she has to get a turn, first... That, and Lilka's the only one with elemental damage, unless you count Lucia's Heat Edge. On the earlier floors, Lucia might have problems with resources, but it's not too bad. Stalling doesn't work because of her, but that's a small liability anyway.