I don't really think it matters whether or not the classes are perfectly even.
I get why they do it for like, the Mario and Sonic games, because they want to sort of create parallels between the franchises, but for Mario Sports I think they should just make characters be whatever role fits them. Which is why I love that Rosalina is Power. I mean realistically, she could fit any class in the game, but Power is the coolest one for her IMO, and they really emphasise it in her graceful yet powerful animations.
Speaking of which, I really hope Rosalina is a Power character in Rio Olympics, JUST so I can say she's one of the best rugby players in the game.