I've known people who were both frontliners and magic-users.

[See: Elsword, for one.]

But it's not so much that as it was the experience, I suppose. There's a reason soldiers are assigned to specific squads and go through so many drills together. It's about discipline, knowing your job in a group, and doing it even if you can indeed do other things than what's ordered. That sort of thing tends to separate soldiers from trained civilians.

Throwing so many of us together like that... at least we didn't end up at odds with each other.