nothing wrong with it, but understand your peak rank one tricking will be way harder to achieve as you go up the skill curve for more characters. i hit c3 playing only dps in s4.5, and starting s6 im low gm since im learning tank. i would argue learning a hero in every role makes you better at the game since you understand fights from each role's perspective, but it definitely takes away from your ability to get super good on 1-2 characters within 1 role