Mercy currently does 55hps on an uninterruptable healing beam. Anything more than 60, I feel, fundamentally breaks her healing vs. effort to apply it. Mercy’s healing isn’t as much the issue with her compared to other healers. Mercy’s utility in damage boost and resurrect more or less just isn’t enough to keep her competitive with the other supports. Resurrect is theoretically more powerful in a 5v5, but with one less person on the team to protect her during it, it can be more of a liability than ever.
The problem with Mercy, in the past and now, is that she can only do one thing at a time and she sacrifices her ability to heal to deal damage and vice versa. The compensation is supposed to be that damage boost makes up her inability to deal damage, but she only averages like 2000 damage boosted per 10 minutes, which is less than any other support can dole out in the same time.
Mercy either needs to be able to swap weapons faster to allow her to dynamically swap between healing and dealing damage, or they could give her the ability to duel wield on a cooldown and then let her swap weapons normally when it’s on cooldown. That way, Mercy has the opportunity to contribute damage to the team but it doesn’t hinder her ability to heal. They could even disable damage boost during the dual-wield and put shoot button onto right click.
This wouldn’t drastically change Mercy’s playstyle most of the time, but it opens up her skill ceiling a lot more as people who can aim will get more value from her ability to multitask.