Okay, list of problems:
300 DPS doesn’t mean squat when Rhino’s minigun has enormous recoil.
Decreasing that recoil would cause worse problems.
Rhino should have abilities which could give him more of a competitive advantage.
People are still concerned about pubs.
Rhino’s a generic high-CQ-DPS character; Heavy at least can multiclass into Medic.
Rhino’s best strategy is fat scout.
Therefore, make Rhino able to do fat scout more easily, so that in competitive he could become a much better character to use.