I mean, technically proven she can outheal mercy if mechanically played correctly, but you're looking at being able to mechanically perfect a champion 100 percent of the time. I see and play moira more often than mercy because people are adapting to her soon to be changes to the live, but even if she can, to me Mercy is still to good to rez someone in a fight. My opinion may change in once the changes go live. But as it stands I see mercy being a constant staple for that reason, and both being played together due to the high healing, and the rez.