https://www.pcgamer.com/overwatch-mercy-nerf-2018/

An upcoming Overwatch update will bring about some big balance changes to nearly all of the game's support heroes, in order to "keep them competitive with each other," developer Geoff Goodman revealed on the Blizzard forums today. And what that means, it seems, is buffing most of them and dialing back Mercy so that maybe someone else will get picked once in awhile. 

Ana, Brigitte, Lucio, and Moira will all be tweaked to some extent, but Mercy is the primary target: The effectiveness of her primary fire healing beam will be reduced by 17 percent, from 60 HP per second to 50.