Hanzo I don't see too much of an issue with.
Winston I think his fine, his not meant to kill players, he is there as a large distraction with excellent mobility. You engage with Winston and while everyone is distracted the rest of the team come in and wipe the rest of the team. His also great at killing mercy.
I think some tanks being slow is fine, like above you need to have a speed boost at the correct time.
Farah I think shes just fine, she still does serious damage. The problem with buffing here is it has a huge knock on too everything else. If she gets stronger then Rin shield starts to become useless and Rin will drop out of the game.
Turrets I think people just need to be smart and communicate better. Few times I've played with people from here we just call out the turrets and have someone tank it like Dva while we focus it down and its not a huge issue.
Roadhog I have mixed feelings, I don't think its annoying that it has amazing range.
Finally I think predictable maps are a good thing to some extent, this is a competitive game and know every inch of the map makes it more interesting," oh there are 6 routes someone could come attack me but from my experience people typically go this way so I will be ready here to counter that". etc etc.