You said impact, not meta. Impact is getting value in game. Meta is the playstyle balance in the game currently favors. You don’t have to be meta to have impact, which doesn’t change the fact that Reaper and Mei were meta shortly before and well into the role queue era. Reaper has a low skill floor, so getting impact out of him is easy for new players, and a veteran Reaper will certainly turn the game if they have good-to-average skill and game sense. Mei used to be exactly the same way, slowing enemies and doing damage simply by waving her hair drier at them. She requires more skill now, but she can still have enormous impact, particularly if her wall placement is smart.
Yes, she was part of the reason double barrier was a thing. Sigma and Orisa alone would not have been able to hold off an aggressive team with just one barrier. Reaper and especially Mei used to punish aggression with ease.
I’m sure being practically immune to poke damage had nothing to do with it. And if Orisa and Sigma’s cooldowns were what made them strong and “nothing” about them was nerfed, why are their pick rates 0.99% and 1.44% compared to Rein’s 12.52%?
I literally can’t even.
I just explained instances in which it has. Twice. It doesn’t happen nearly as often as tanks, but I already explained how meta influence and in-game impact are not the same thing. And none of that is even relevant to the still-standing fact that when tanks or supports influence the meta, people complain loudly and they get nerfed, often quite hard.
So, again, damage has impact, and the damage roster is not the unique victim of unwarranted nerfs and balance over-corrections.
Peace. 
