Sorry to break it to you but Mercy is nowhere near as powerful to warrant a nerf. Her stats are also just average at best, even when her favorite pocket (Sojourn) is literally running every lobby by herself.
She needs no nerfs, you just need to learn how to play against her
See, I hate having mercy on my team. Unless the other support is doing overtime, we generally suffer on the end of healing/sustain. Blizzard could literally make mercy bots to take part in games and I would have a hard time telling them apart from the average mercy main in all seriousness. In ow1, they did have the movement tech that could be used to escape but its much more difficult in ow2 to see the impact of mercy outside of a soj or ashe damage boost.
So what you’re saying is there should be a mini game like Mei’s Snowball Offensive but it’s throwing burgers into enemy Mercy’s mouth until she pops like an overinflated balloon at the carnival.
The only thing I’d ever advocate for her is that she should get her revive to reset when triggering Valk and she needs to lose the damage beam for something else. It causes too much problems.