I’m baffled at your argument that Rein is op because of his high pick rate but Dva is not, because she can do her job. (?)
Dva is an incredibly flexible hero that fits in every composition.
Mainly due to her DM, mobility and good damage output.
Doesn’t matter what comp you run, Dva is nearly always included in it.
Look at OWL WC, 98% pick rate compared to 33% of Rein and 57% of Winston.
Is she op currently? No I don’t think she is,but she is certaintly very strong.
Now to Rein. To avoid making this post massive, here is what I wrote:
(TL;DR version)
Basically there are not enough options to choose from if you want a main tank.
Winston is for dive and you got just Rein and Orisa if you want a barrier for a less mobile army. Orisa has a more defensive nature, so if you are attacking you are more likely to pick a Rein. This is why Reinhardt is picked more.
Reinhardt is a melee hero with an abundance of weaknesses and requires you to pick certain heroes in your team to enable him.
Without a lucio for speed and a zarya to support him, Reinhardt is so much less effective that you may as well pick Winston or Orisa.
Add to that Brigitte and you allow him to excel in a brawl fight.
His charge ability is high risk,high reward, very telegraphed and has an auditory warning that he is starting to charge.
His ultimate also has a long telegraphed animation and auditory warning that it’s going to happen giving enough time to everyone to either cc him,cancel it, block it or avoid it.
He is the only other hero alongside lucio that is very vurnerable during casting of his ultimate.
All of his abilities feel fair, balanced and rewarding to use.
The hero is not oppressive, he is strong at close range, but very vulnerable to cc and easy to overcome/avoid with mobility.
There is a reason Dive was king for so long. It just happens that now with Brigitte, there are more Rein-enabled compositions.