You mark an ally for 10 seconds, if he dies during this time he revives instantly, if he doesn't you just lot a bunch of mana for nothing. This spell was present in White Mages of most FFs, it would be interesting to have this in the game. It would work as a backup tank invulnerability, but signifcantly worse because dying is still very bad. If there's a hard mechanic going down or a large dungeon pull and your tank doesn't have invul up, it might be wise using Reraise. In a way it works just like a shield but for Raise.
What do you think? Would there be any way to exploit an ability like this? What about the same but for Esuna ("Resuna")?