I wouldn’t say a majority of Mercy mains would want the old ultimate back. Personally, and among many others I’ve spoken to about it, the old mass rez was horrendous. It encouraged a ridiculous type of gameplay—run and hide, and not to mention, you were held extremely accountable if you failed to do so.
Valkyrie is a good ult, there just needs to be tweaks made. For some reason Blizzard refuses to remove rez. I’m not sure if it’s because they can’t come up with a good replacement, or if the rez is far too tied into the lore for Mercy, but they would rather sacrifice things like her healing capability or the chance to be creative with something new, rather than remove rez.
In most situations she’s kind of a bad pick now. I can barely see her as a primary healer anymore, which is unfortunate, because she was really the only, truly dedicated healer before (since you have Moira that needs to DPS to continue healing, and Ana players tend to be a little trigger happy when it comes to DPSing as well, though you can’t blame them to occasionally take shots).
It’s been a while since the 50 HP nerf. I’m not sure if Blizzard plans on making certain changes unless a new hero makes it that she NEEDS a change even more than she already does. Hope for the best?