I've yet to find a Mobula that is truly over powered. Sure I've fought some that are agonizingly annoying to deal with, but then I go rage and focus on that Mobula. In a one on one, I can either outmaneuver or outgun them, depending on the ship. I only ever really have trouble fighting one when I'm fighting his ally and he pops in as support, or is camping a spot with his ally.
As a brawler, the ship is underpowered, but as support, it's overpowered. I think this balances it nicely.