I think that it’s safe to say that mercy with rez on a cooldown can’t be tweaked to make her balanced and a great pick at the same time. The reason why is because giving a hero that can result in man advantages with an ability on a cooldown without even earning it is just op. This ability is so op that many other parts of mercy’s kit had to be nerfed. If you would want to balance this ability, either make this ability need ult charge to obtain or put mercy’s resurrect as an ultimate with a few tweaks.
One way of balancing rez is to look at the ideas posted for mercy that have been ignored for a pretty long time and some of them have ideas with the potential to make her more balanced, fun and a better pick. Some ideas for mercy that people have posted on the forums about could be tested on ptr to see if people enjoy the change or not. If you still think that mercy’s fine the way she is currently well some mercy mains have mained other heroes and the main reason was due to mercy requiring so many nerfs that she couldn’t even keep up with the pace of the game and as a result you could most of the time get more value as other supports rather than mercy. Recently, many people I’ve had in my games hate the idea of having a mercy on their team due to other supports having, I even had one of my friends hate playing with me because of the fact that I one-trick mercy.
Another way of balancing rez is to bring back mass rez, even though it was an ultimate disliked by many, it’s similar to a zen transcendence in a way, the difference is that zen saves them and the enemy team can’t kill things easily there, mercy’s rez is similar to trans except that it would create the illusion that they had already won the fight, but mercy brings back her allies back from the dead and you have a chance at killing their enemy mercy. Both of these ults have counter play such as killing the mercy first or having another team wipe after the ult (similar with zen such as you may try to force out trans, kill zen or use ults after trans).
Rez should be an earned ability or even taken out of the game because mercy’s rez having a cooldown is the reason as to why she’s been getting many nerfs. But I know that Blizzard wants to keep Mercy’s rez in the game so I think that your best option is to either test out the ideas other people have provided and try them out on ptr, or bring back mass rez without invulnerability, with a line of sight, and cast time. If these aren’t ideas that you’d like to do then take out rez because I don’t think that many people would mind if it was in the game or not. All I want at the end of the day is for mercy to be a good enough support to keep up with the value that other supports bring and also that she becomes more fun.
Thank you for reading this.