It seems like Jeff just hates her.
She’s the most nerfed hero in the game (If you count her first rework). They keep nerfing her and it might come to a point when you will never see her in a game. I think that when she uses her ultimate, her resurrect’s CD will be 15 or 20 seconds instead of 30. Also I think that she needs to do more damage while in her ultimate. For some reason they nerfed her healing to do 50 per second instead of 60, this caused her to have silver medal at healing when having a brig in her team. The only way you can still play Mercy, have fun and win the game is by going triple healers or Phara - Mercy with another main healer in the team.
Mercy was one of the most picked heroes in the game if not the most one and it changed because of that. I can understand her first nerfs but it got to a level when it’s too much.
Mercy is still the 6th most picked hero and forsure in the top 10 heroes. Let’s not waste time on her and help the rest of the less played heroes. Cause you know its fair to do so. Atm you will see mercy exactly x17.8 times then something like bastion, how’s that fair?
Jeff doesn’t hate her, he’s just failing at his job as a designer, which is okay, people fail all the time, he’s only a soft, squishy human after all. It’s our responsibility to teach him good design until he fixes the mess he made. 
The reason they’ve nerfed her healing is an attempt to balance her kit around the existence of res, which they’ve struggled to implement in a smart way since forever. They’ve implemented a terrible design element in the cast time and since that still wasn’t enough, they’ve had to start gutting Mercys healing output, which makes certain flaws in that area of her design even more apparent.
Well, fun is causality. You do this, so this occurs and that results either a victory or a loss. You learn from your mistakes and thus revel in your successes. That’s fun.
There are far less opportunities for Mercy to make an actual difference to the flow of a battle now. She is denied the chance to make decisions to help achieve victory beyond utilising her mobility which will only get her so far. So that makes her drastically less fun to play.
This is just hot air and doesn’t help anything. The solution to a problem is not to just give up on it and focus on other things because you weren’t able to fix the problem to begin with. It is not the fault of Mercy players that the devs have had a hard time designing / balancing her. We have given a lot of advise to the dev team, but they’ve stubbornly made mistake after mistake, but that’s their fault, not ours.
If you’re interested, there are several other threads about Mercy and her balancing patches. Those 3 are the most discussed ones.
The Truth about The Mercy Nerf - #13 by Wickedlike-2109
The problem with Mercy
Addressing Mercy nerfs
Also, as a piece of advice, please look for similar threads and continue the discussion there before posting a dublicate one. Duplicate threads make the Forum chaotic and are actually against the CoC.
hog, widow, hanzo, and fist need way more attention and tweaking.
That’s fair because there are what? 15 damage heroes and 6 supports? That’s almost 3x as much damage heroes as there are support heroes.
No need for buffs, simply nerf Ana because right now she is a monster. The best support in the game by far, similar to Mercy’s situation.
Ana is fine the way she is. Actually, the sole reason Ana has become more prominent is her nano buff and Mercy’s latest nerf, which coupled together felt like a big buff to her, but she’s fine the way she is tbh. Mercy needs changing. She needs to 1-Stop being an annoying flying moth that regens health every sec 2-Stop being an off healer. 3-Stop having Resurrect every 30 seconds.
By this logic when Mercy was the undisputed best healer she was fine too.
No, Ana is not fine, she needs nerfs instead of this whole BS favoritism. Enough is enough.
When I play Mercy I don’t have such fun as I used to have before and I feel like she is weak pick. I still want to play her because of her being Mercy and looking lovely to me. Truth is I don’t play OW quite as often as I used to prior to her healing nerf. It’s just not fun anymore.
So basically your argument is make Mercy not Mercy.
If you remove those 3 points you have against Mercy what else is she left with? Literally just left and right click lol. Of course you didn’t mean remove res altogether so what… 1 res every 2 mins that can still be cancelled by freeze, hacks, hooks, boops and stuns etc?
Give it a rest. Seriously. They can’t snap their fingers and make a balanced solution that everyone is happy with.
Maybe just stop being so self-entitled? Other heroes have been bad for longer and are way worse than Mugsy is. There’s no reason for Mercy to jump the queue.