I did a lot of flying on the Mobula over the weekend. I found it to balanced just about right. Only complaint I ever really heard was, "I really wish there were ladders back here."
Now that I've found a build I like, a lot, a whole lot, like most fun I've had since I started playing the game, I really enjoy the Mobula and find it isn't nearly as bad to engineer and all that as I first thought. It's just a ship that operates a good bit differently than the other ships.
Comparisons to the Spire are not correct. The Mobula is the glass cannon the Spire maybe should have been.
I find that the only repairing to be done is right after you kill whatever is trying to kill you. Otherwise you'll just die on the way to the hull.