My highest level dude is level 6 even though I play everyday. Leveling gets slow around 5 (which is a good thing, balance becomes better). But anyway I've been lucky enough to get all the characters, so I've got plenty of teams that we could fight at even levels at!
Also,
Dante Trailer. Still doesn't seem to be available in-game, so I dunno but they're acting like he's in now. I did fight against him in a mission though.
Edit : Oh wait, he is unlockable in-game now! Cool!