Or at least more impactful or fun again.
Suggestions:
1-Give Valkyrie one instant rez.
2-Make Valkyrie an E ability and bring Mass Rez back with MAJOR tweaks.
3- Give Valkyrie Purple Beam (heal and damage boost at the same time)
4- Make rez an earned Ability.
5- They could also maybe make rez let multiple people who are no further than 5m from each other be resurrected too. You could maybe make that happen only during Valkyrie.
6- Give rez shorter CD during Valkyrie
7- Remove Rez as an ability and give her Purple Beams as an E, and bind Rez to the activation of Valkyrie. By doing that Mercy could Multi-Res 2 people instantly and continue on as current Valkyrie.
8- Make Rez a channeled ultimate where if Mercy keeps channeling one person after another gets razzed. Making Valkyrie an E ability.
Anything is better than how non-impactful, not fun, and unsatisfying Mercy is right now.