I think matchmaking needs to be improved, I almost always join games where its a complete massacre and end up getting frustrated with the game. I just can't seem to find good games after level 20.

Also the whole being able to have more than 1 of the same hero thing needs to go. It gets way too out of hand and is more frustrating than fun.

Bastion's turret mode needs some sort of nerf. He either needs less health in that mode, less damage, or less accuracy or perhaps he can't self heal in that mode. He needs something to make him more skillful than lying down and firing down a lane. Yes you can knock him out of it or deflect it but when he's tucked away and protected by his team he is a serious problem.

The AI on Torbjorn's turrents needs to be dumbed down a little bit. Perhaps a range nerf? A small damage nerf wouldn't hurt either.

Symmetra's sentry turrets need be capped to 1, maybe 2 turrets at most. Her being able to slap that anywhere is too strong. She must be like Torbjorn and force to pick where is ideally the best spot for them.

Other than that, I think the game is balanced everywhere else. Mostly the issue is characters with turrets that are just too powerful. They are hard to deal with and can seriously destroy teams with ease. Hell with Torbjorn I essentially single handedly stopped the enemies from delivering the payload by putting the turret at a distance where I can repair it easily and its hard for them to hit. Whenever they pushed as a group I hit the ult and pushed them back. Turrents shouldn't be capable of getting triple or even quad kills with ease. And that was just one Torbjorn doing work. More than that is just too powerful for defense more times than not. That's just my thoughts after about 15 hours of game time.