We have two mages here as well, but the wizard is really the more academic type, while the sorceress is the more intuitive type. Of course, the ranger and rogue also have non-magical combat skills, while only two have magic.

As for the bard, she can fight but is really more of a "diplomat." If this were a D&D game, she'd be handling the bluff and diplomacy checks. And a lot of other things outside of a fight. 

And the OP thing is a good point. This is a team game, and having one guy outclass the others is a problem. Not that tiers are necessarily a bad thing. Even the MCU Avengers have an upper and lower tier: Hulk, Thor, and Iron Man are leagues ahead of Captain America, Hawkeye, and Black Widow.