That's right, and it's something I forgot about. Her pistol isn't hitscan (that is, the projectiles have travel time and can thus be avoided) but it fires exactly where the crosshairs are pointed, without fail. I wasn't aware of her pistol being stronger than you'd think per shot though, nor her quick-like-a-bunny-ness, though she definitely has what may be the smallest or second smallest hitbox - she's a tiny little thing - which certainly helps her survivability outside her mech. Otherwise one, definitely two, solid shots from Reaper would put her down.IN her Meka, D.Va has one of the biggest hit boxes of all characters, and unlike Roadhog, who may actually be even bigger, I don't think she can heal herself. Of course, Roadhog can't Jump out of himself and run away, to call down a whole new him and resume battle.
You could probably match her most closely with Winston, in terms of....general features, I suppose when she's in her Meka - they both have boost/limited flight, they're both surprisingly speedy for being so huge, they're both big bullet sponges, and they both have rather short range weapons (though Winston's Tesla gun has an actual 'it will not go past this point' range rather than 'you effectively can't hit past this point because shotgun spread' range)! And both (effectively) receive a full health restore with their Ultimate (though D.Vas is more situational and may require a second use).
At least it's hard to tell quite where to get a headshot on D.Va's Meka is, though by the same token, it also seems to be up front kind of in the middle of the 'torso' so maybe she's a lot easier to peg there in normal combat. She's set up kind of like a Battletech Timber Wolf, or ED-209, rather than your Standard Anime Power Armor (or Hulkbuster suit)