I have not seen this in this thread, nor in recent ones about Mercy. But I may not have read everything that was said.
This is perfectly fair and understandable. It’s super irritating when Mercy gets the rez on the kill you just secured. It’s super irritating when she can fly around the map and is very hard to target and bring down. It’s super irritating when she boosts another hero and makes him more powerful, especially if that hero is already very powerful (hello Sojourn / Freja and others). That is true, 100%.
The question is : can we do something about it ? I suggested either : 1) making boost a ressource based ability with an internal timer : you can only boost a hero for a few seconds, then that ability is locked on this teammate for quite some time or 2) make it boost something else : not attack speed (that would be kinda the same), but maybe CD speed recovery, or movement speed, or something like that. Something useful but not too strong. Something that aligns with her “pacifist” mentality.
Rez is kinda of her “thing”. I’m not opposed to removing it and replacing it with a powerful burst heal, for ex. That would encourage Mercy to move around more, be more vulnerable because she has to move around instead of pocketing from relative safety.