I think Mcree is fine and doesn't need to be nerfed ( Just looking for civil discussion no need to downvote yet).

He exists entirely to annhilate Tracer and Genji and frankly I think Tracer is far more annoying than Mcree because of how much escape potential she has while a good Genji is pretty much carries matches.

Mcree has obvious weaknesses that are very easy to exploit. Mediocre mobility and his ult is extremly easy to interupt.

Deadeye weaknesses: only 15-20% of Deadeyes will actually kill more than 3 enemies. It's best used to finish of low health enemies. More importantly yes it can zone enemies but getting behind a Reinhardt shield will still let you be in a fight and kill him. He is also pretty much stationary/super slow so Roadhog can hook-instakill him or Genji/Pharah can flank.

He is weak against long range snipers and Bastion can mow him down unless he is really close.

Also sometimes he is pretty much unbeatable 1v1 but a Roadhog/Reinhardt/Zarya combined with Mei/Reaper will beat him easily as long as the tank baits Mcree stun. His fan the hammer isn't that accurate from medium range.