Make her game play more fluid by reducing that dang 1.75 second cast time. Mercy got Invulnerability during Mass Rez era because she kept dying on Rez, but even that was a good trade-off since it got the team back when Mercy died. 1.75 second cast time is killer, an over half the time no Rez occurs.
For the rest, maybe some suggestions from the top of this thread-