This past weekend, I played a lot of D. Va. Previously, she was probably my least used tank.
I changed my approach for her, however, as she's not really a tank and more of a distraction, IMO. Fly in, cause some havoc and do some call outs, fly out and repeat. When you're out of your mech, do the best to get some damage in (her gun is surprisingly good, especially with headshot damage) and wait to get your mech back.
She's a lot better than I remember and can be really helpful on certain maps. My favorite is probably KOTH because that's where I have the best luck with her. In particular, on Ilios, I had the entire enemy team yelling at me because I would pop in at the Lighthouse, bonk them off, and then float away. Great time right there.
She does suffer from any sort of damage in her mech, I feel like. If you're close and you go for the head, you can deal damage, but if it's any offensive hero or any moderate damage hero you're going up against, you're going to have a bad time. I can only imagine what she'll be like in good hands after a buff.
It also makes me sad how good people are getting at avoiding her ult. (Plus, I'm really bad with it currently.)