Riot has announced that the bug with "The Show Goes On" K/DA event quest has been fixed!

Previously, you were unable to earn progression for the quest by reviving 60 units and instead were required to target 100 enemies. For those Shadow Isles fans who have not yet completed the quest, have fun!

Quote From RiotRaptorr

Unless they fixed it the revive part is bugged completely. If you wanna do it then go and target enemies

That issue should be fixed now! :)