Overwatch's hero Mercy could be one of the most frustrating characters in the game. Not only could she heal her teammates, she could revive them too. Having all your hard work erased as everyone on the opposing team is brought back to life by Mercy's resurrection ultimate has been one of the saddest things about the game for a while now. Finally, Blizzard is bringing some patches that will totally change how Mercy works.
First, the resurrection ability is being moved from an ult to a secondary ability. Instead of potentially bringing back the whole team, its use will now be limited to one person and it will have a longer cooldown time once used. This makes it much less powerful but it will be useable in several different situations instead of people just hiding away waiting to use their ultimate.
Mercy's new ult is called Valkyrie and it comes with a load of benefits. First, Mercy will be get full, sustained flight. She will additionally get most of her stats boosted. She'll resurrect quicker, her healing beam will reach farther, and her gone will shoot harder and faster.
This sounds well and good but there may be some issues. This ultimate gives a big advantage to Mercy which is only increased if she's under the effects of Ana's Nano Boost ultimate. This combination has made Mercy almost unstoppable. Rather than resurrecting her own team, it's now almost a breeze to kill the entire other team instead. Obviously, this isn't really a balance – it's replacing one op ultimate for another.
The Overwatch team is already aware of the issues with Mercy in the PTR update and they've said they are looking to make some adjustments. Currently, some lead designers are suggesting that it's just the gun that is too powerful. Mercy isn't really supposed to be primarily a killer but with so many stats boosts, that's what she becomes. This isn't abnormal though. Big adjustments like this always take some test time and tweaking to get right, and that will undoubtedly be the case here.
You can watch Game director Jeff Kaplan talk about some of the past problems with Mercy and what they're doing to fix it here.