S… strong utility? You mean the single target resurrection that disables your healing for almost 3 seconds? How is that strong utility?
You’re switching out another healer with actual utility (Speed boost, weakness increase, sleep dart, healing increase/negation, all of Brigitte…) for a character that every 30 seconds resurrects one ally (Not warranted, because the cast time actually makes some allies unable to be resurrected due to where they died), when others can apply their utility much easier, in a much shorter cooldown.
If your ally died and you resurrect them, during the next 30 seconds, your team is with a subpar healer with no utility.
- Zen can still weaken your team so you fall quicker.
- Ana can still negate your healing easily, and with some skill, even sleep someone (which is pretty much a death sentence).
- Lúcio can still speed you up to help you dodge and get through choke points so you can position more easily on favorable positions.
- Brigitte does… whatever she does. She can mitigate some damage, she can stun someone (Which, even without a team, she can make that a death sentence by herself in 1v1 scenarios), she can push back people, emergency heal that applies armor, in-combat healing…
- What Moira lacks in utility, she has it in raw damage, making kill secures easier and flankers less of a problem.
All of them - with the only exception of Lúcio - can apply their utility while they heal, and they all have their utility on a shorter cooldown than resurrection. With how little Mercy heals (and considering she can only heal and also considering she has to stop healing to resurrect), there’s no reason to pick her over another healer. At all.
It’s easier to win the fight when you can disable enemies and cancel their healing than with a subpar healer that resets the fight after the first ally is dead. If your team isn’t already ahead so you can keep the momentum with the resurrect, you not only can’t help to make a comeback, but you’d be better of switching characters, because the only thing you’re doing is extending an unfavorable situation.
As I already said before, undoing death might be more frustrating to play against due to how our brain works, but…
Preventing deaths is always more effective than undoing them.