If you’re interested, there are several other threads about Mercy and her balancing patches. Those 3 are the most discussed ones.
The Truth about The Mercy Nerf - #13 by Wickedlike-2109
The problem with Mercy
Addressing Mercy nerfs
Also, as a piece of advice, please look for similar threads and continue the discussion there before posting a dublicate one. Duplicate threads make the Forum chaotic and are actually against the CoC.