She's the youngest hero in Overwatch, but she is potentially the mightiest of them all.
If you've been playing Overwatch for a while you may have noticed just how often D.Va gets picked; attack, defense, King of the Hill, quick play, competitive...
You name a situation and D.Va will - in the right hands - probably be the most useful asset of your team composition.
"But she was nerfed!" you might say.
Yes, her armor/health ratio was re-balanced so that she can't waltz into a fight, take all the damage while she shoots everyone in the face with unlimited laser ammo, and then fly away like she was never there.
My opinion as someone who has been playing D.Va for 100 hours: it's more fun this way. Trust me.
But how is she still so great? Let me explain:
She's Versatile
Firstly, D.Va can fly in any direction.
This ability makes her as much of a threat in the air as she is on the ground and causes Soldier, McCree, Widowmaker, Hanzo, and Pharah to be significantly less effective because they cannot hold their high-ground positions against a badgering D.Va. She can use her boost to knock them down while doing melee damage in the process.
Her boost is also powerful when she needs to push an enemy towards a certain direction: off of a ledge for an elemental kill, into a secluded corner for a focus kill, or off the point for a quick capture.
Secondly, D.Va's ammo is infinite.
Some people think this makes her over-powered but they don't realize that she does little to no damage at a distance; D.Va is a close-range hero which makes her essential in composed and impenetrable group attacks since most enemies find it difficult to hide from a face-full of lasers at point-blank range.
Additionally, D.Va's Defense Matrix protects her teammates, specifically healers.
In many cases D.Va players have a sixth-sense that helps them notice where they are needed most. A flanking Tracer, Sombra, or Genji will find it difficult to focus healers that are protected by an attentive D.Va. Other scenarios that require quick defense can be dealt with with a quick button-click that pulls her Matrix up for a couple seconds but doesn't deplete much of its charge.
She Destroys Ultimates
D.Va's Defense Matrix has the most powerful ultimate countering abilities in the game: if she can get to the right place at the right time, she'll turn the tide of a fight or even the entire match.
For example, Tracer's Pulse Bomb, Mei's Blizzard, and Zarya's Graviton will disappear if they accidentally throw it into D.Va's Matrix which can prevent an entire team kill from enemy ultimate combinations.
Hit-scan ultimates such as Soldier's Tactical Visor and McCree's Dead-eye are easily countered by a D.Va with a fully charged Matrix who knows how to get up in their face until her team is safe.
She Has Two Weapons
"Baby" D.Va may seem squishy outside of her mech but people underestimate her solo abilities. Her pistol's surprising accuracy combined with her tiny body makes her a tricky target to hit.
Many heroes find it extremely difficult to land close-range shots on Baby D.Va because of her minuscule hit-box so a good D.Va player will get right up in the enemy's face and try to land as many head-shots as possible while they scramble around her.
Long-range use of her pistol can do remarkable damage to unsuspecting enemies and can take out a stationary Soldier or Ana with full health in four or five headshots. It's the perfect weapon for checking for unwary flankers who didn't realize 12 laser bullets were headed their direction as they entered a doorway.