Been a mercy main for years. You can dish out big healing in the right games and rez is obviously broken. But she just seems outclassed by so many other supports right now. I don’t really know what can be done for her, but perhaps some sort of AoE healing option or a buff to her blaster could help I think.
Support right now is defined by their self agency/Dueling potential with damage. Unfortunately, Mercy and Lucio are both way more team-play based ans struggle as a result.