So Dva is garbage, right?
I like her a lot. I've played her a bunch since she came out and I have a 62% win rate with her at ~3k MMR (if people still trust hotslogs) in QM. Granted, some of that might be due to my not having played QM in over a year, so my rating has decayed and I'm still climbing. But two things make me think that she's actually really good.
First, I feel like she's really good at making plays. She has a lot of weird control that the other team has a very hard time dealing with. She can start a fight with booster, if someone runs away she can boost past them and turn around to knock them back into her team, she can boost in and knock people away to help a friend escape, defense matrix can make it very hard for their damage dealers to hurt her squishy friends, and then she has incredible area denial with self-destruct. I can start fights, I can end fights, I can make the enemy team all run away, and I can negate 75% of probably two heroes' damage in a fight.
Second, I screw up a lot. In a typical game I die at least twice in a way that was totally avoidable, so even though I'm already doing pretty well with her I could be doing a lot better. And with D.Va, screwing up really, really hurts. With other heroes if you mistime something you'll take some extra damage or miss out on some damage, and sure maybe you'll die or miss a kill, but typically the outcome of the fight doesn't end up being
that different. With D.Va, the difference is very often your team wiping theirs and taking few or no losses versus the opposite -- it feels like Zeratul with Void Prison. If you can tank some damage, activate self-destruct in a good location, and live for four seconds, your team is winning the fight. You'll be back in your mech with full HP ready to bully a scattered enemy team. If you don't activate self-destruct in time, the enemy team has no reason to run and you don't get your mech back in four seconds anyway, so they pop you and then turn on your team.
I also really like how different her two modes are, and there's a lot of strategy in when you let the mech die or use self-destruct, and then when to reactivate the mech. D.Va in the mech is fine for clearing minions but has awful single-target damage. D.Va on foot has good damage which turns incredible at level 16, when she can tear down a keep
very quickly. Likewise for enemy heroes -- you can get a few kills from assassins popping the mech and then you just stand and shoot them instead of running. With the right level 16 and 20 talents you will often want to let the mech die so that you can come out and take some shots on foot before calling a new mech down on an enemy's head. She can have some sweet Li-Ming type moments where she's up against several enemies and ends up killing a few of them and getting away because of the way kills on foot can refresh the mech.