Secondary Tanks that work well with D.va are Rein and Zarya. With Rein, you can focus on damaging out the other team, and only have to really use your wall for blocking ults and heavy attacks.

Zarya is somewhat the same, easier to dive with imo.

I don't really die much as D.va, since I play in group with my team and usually never really take to much damage because I have my DM timing up well. But I actually prefer Mercy/Lucio combo. I think Zen is fine, but I don't think he's really got anything that really helps D.va perform. Lucio with a healing aura and Mercy with a damage boost keeps a backline D.va's DPS at an outstanding sustain.

Ult spots are VERY important. I love the long road on Dorado outside the church. It's a great place to throw ults. I feel like D.va ults work good when thrown over walls (hollywood, eichenwalde) or thrown down long roads (Dorado, Route 66 last point)

As for VODs, I've seen plenty of great ones but never one that really made me excited or proud of the player. Last night I was live spectating a D.va I'm coaching and they were doing a lot of what I was suggesting and I watched them go from losing matches in a row to really grinding up and winning every match for the rest of the night. Because of how split D.va is, it's hard for someone to show all of her potential in a single match. Some nights, I don't even have to use my DM because we'll have a triple tank comp (rein/zarya) and I can let them handle everything while I just grab highground and dps the enemy team down.