Overwatch has been around for a little over half a year now, it has gone through a number of balance patches and yet the game is in such a terrible state for balancing, it's quite shocking that a game can be this unbalanced when there's only 23 characters to take into consideration, while a game like Dota2 that has a little over 100 characters has much better overall balance.
What Blizzard have been doing with their game (which they also stated their self in 1 way or another) is that they're trying to keep the game balanced for both casual and pro players, the result so far is that about 60% of their roster is very under-used or not used at all. Lower tier players will consider characters such as Torbjorn, Symmetra and Bastion to be very strong characters, where as higher tier players will consider them weak, situational picks or just completely useless, the difference of opinion is so strong and yet Blizzard are trying to focus their efforts to potentially buff these 3 weaker characters, but not so much in which they will dominate the lower tier. The idea behind that kind of balancing is good for the casual scene, but it leaves the higher tier/pro scene character picks in constant jeopardy.
Let's take Mercy and Ana into the easy example here; they are both single target healers with their own strengths and weaknesses, the major differences is that one is a lock-on regen healer with low/medium range distance, and the other is an infinite range accuracy required burst healer with the ability for even larger heals with her biotic grenade. I always hear the argument with Ana which is "yeah but Ana requires good accuracy whereas Mercy doesn't", to which I've always responded that once you're going up against high accuracy players...well, that argument gets thrown out of the window and we end up with a meta in which Ana dominates while Mercy is left on the bench.
Mercy in lower level play see's very high usage because of the fact that she gives strong heals without having to directly aim, playing her at a low tier/casual level offers rewarding enough gameplay in that you can make a good enough impact on the game by simply healing and resing when ever you can, even if those resurrects don't actually accomplish a great deal. Ana on the other hand doesn't see much play at that level because she requires good accuracy to hit enemies and effectively land your heals, if you don't land about 60-70% of your heals at minimal, then you end up effectively healing less than Mercy.
What should be happening is Blizzard need to be balancing the game taking raw character stats into consideration and how high level players are dealing with the game balance, then they should be heavily considering their feedback. If Blizzard is going to continue going off of their gameplay stats while consistently taking low level players into consideration, the only thing that's going to happen is the game will continue to stagnate and the pro scene will get so boring to watch in that the viewer count can only really drop and prize pool won't have much chance for getting any bigger.
Outside of how Blizzard have been balancing, the other issue is how slow they go about it. A big disappointment was the introduction of a massively anticipated and hyped up character that went straight into bottom tier which is nothing short of crazy. Ana started off as what I think was a medium tier character, within a couple months she went straight into high tier, whereas Sombra has remained in low-tier throughout her release.
My only hopes with Overwatch now is that Blizzard will eventually start to properly balance their game and at a much quicker rate, they don't take enough player feedback into account either which has been nothing short of frustrating for players, and their PTR is nothing more than a stability testing grounds to see if things work. Overwatch is a good game for what it is and it's very clearly riding on the Blizzard name above all else, though that can only last for so long until players start flocking away.