Yeah, I just think people are quick to use "OP" unfairly. "Overpowered" means that she's poorly affecting the game; if her healing was enough to be causing a major shift in win/loss ratios, for instance. In matches where both teams have Mercies, if neither team ever wipes and the clock runs out into OT constantly, that's "bad". If she's just delaying/preventing some team wipes, by preventing a pick from collapsing the team, then she's just acting as a healer hero should; it's not that different to me than a Zarya bubbling the healer who gets hooked by Roadhog, or whatever. It's one rez every 30 seconds; if you cant follow it up with more kills, you weren't winning that teamfight anyway.
Healers have been struggling for a while. I think they could all (minus Mercy, now) use some love. Unless it's pushing teams to run 3-4 healers, I don't really see how they'd be arguably "overpowered".