First of all, let me clarify that I don’t main Mercy and hardly play support at all; I’m a Bastion main, and as such I’m all too familiar with the signs of a character about to hit the brick wall and sink to the bottom of the barrel.
First of all, what’s Mercy all about?
Ultra-consistent heals over time. High mobility, granted teammates are visible.
What are Mercy’s weaknesses?
Frailty, lack of self-defense, burst damage.
50 healing per second?
The wrong nerf, honestly. This actually negatively impacts her strength: consistency. It makes it so even Winston can out-damage her healing, making her a less consistent counter to incoming damage. She’ll be worse in a team fight due to this, and as such becomes only really effective outside of battle. This is an egregious error in game design: making you less effective in the fun and action-packed moments that the game is based around.
What’s the deal with Rez?
Currently (Live), Mercy’s Rez ability is a very polarizing one indeed. You’ll either get “its ok but kinda weak” or “it’s completely broken.” Why? It doesn’t scale in effectiveness as you go up the competitive ladder. On a cooldown, it’s naturally a less interactive ability. How do we fix this?
Conclusion
Mercy is a healer designed for consistency and mobility. Rez is in an awkward state due to its lack of SR scaling, and nerfing her base healing effectively removes her impact during a team fight.
Solution
Keep Mercy at 60 hp/sec. She has to do something useful during a team fight.
Put Rez on a charge meter instead of an uninteractive cooldown. Rez could only be used after a certain amount of damage is amplified or healed. Tone down the downsides of the Rez animation, and put it on a short cooldown if the Rez fails, without using up the charge. Rez has the power of a mini ultimate, and so should have the charge requirement of a mini ultimate.