Because fundamentally her kit is broken at high SR. In lower SR Mercy is played as intended. I think general complaints in lower SR are all things that are super counterable, but Mercy is using a lot of her kit to its fullest; the Mercy player is showing skill on the hero. I’m a GM support player, but I watch my friends stream and do a little coaching as well in gold through master.
A Mercy in mid to lower SR has to pick up a lot of the slack with healing. Your main support, typically an Ana or a Bap, simply does not have the technical skill on such a mechanically demanding hero to keep up with the damage…the off support has to step in. Add to that the fact that lower SR players tend to take a lot more ‘trash damage’ with bad positioning and simply demand more healing than higher SR players, and you have Mercy utilizing her full kit in a meaningful and impactful way. Does she still damage boost? Of course, it’s an important part of her kit. But she has to use other aspects of her kit way more, and make much more thoughtful and risky plays to keep her team up and running. This is high risk, high reward gameplay.
As you climb in ranks, Mercy’s gameplay takes a strange turn. In what I think to be the only hero in the game to do so; the higher in SR you go, the less ability on the hero you need to get value, and the more you are viably encouraged to use less of her kit. I’ll explain.
In higher SR your teammates are able to, through experience and ability, avoid a lot more damage. And your Ana or Bap, as heros who scale with ability, are able to heal a lot more than their lower SR counterparts. Because of that, a Bap or an Ana are reliably to solo-heal their team through most things. This means that Mercy is free to…not use most of her engaging kit, to be honest. In high SR, the best way to climb as the hero, is the meme-y ‘braindead’ way of playing her. Is Mercy the most big-brain hero in the game? No, but she does have a lot of nuances that people disregard sometimes, which you ironically see lower SR players have to use with more success. In high SR you are best rewarded for just hard pocketting a DPS hero. This is how she is mainly played in GM. Meaning, you don’t have to take that high-risk high-reward gameplay; it’s punished. It becomes high-risk low-reward in higher SR, whereas the optimal way to play her to climb -using a small part of her kit and basically ignoring the rest of her team most of the time, hiding behind a DPS and tucked around a corner, out of sight (like Big-Rez Mercy, tbh)- is low-risk, high-reward.
There is no reason to use the majority of her kit as designed. It’s smarter to just sit out of sight, pocketting one person the entire time. This is the complaint people are seeing boil down. It’s really frustrating in GM dealing with this, as this is the Mercy that is difficult to kill. It also punishes intelligent, thoughtful Mercy gameplay, but rewards the brainless gameplay. So there is no distinction between really nutty good Mercy gameplay, and mediocre ‘LMB’ Mercy players. Furthermore, Mercy has minimal control of her own W/L…in higher SR, most of Mercy’s value lies entirely on how well her DPS hero plays, and her pocketting him.
Higher SR players want a rework that adds more options to her damage boost that causes high SR Mercy players to have to be thoughtful for its use. This will allow for a much broader range of Mercy play, and reward really good players, and since damage boost is not entirely Mercy kit in lower SR, it wouldn’t affect them nearly as much. It’s intended to raise the skill ceiling for the hero, and particularly affect the top percent of players.
There is even precedent for this; Lucio was reworked in 2017 specifically citing that he was not being played as intended to the full extent of his kit. He had this interesting kit with all this mobility, but using it was high risk…whereas if you just sat as a ‘heal-bot’ (or even speed-bot) far behind the team, from a point of total safety…you could do the same thing. So of course this is how players played him; it is dumb to take extra chances and make risker plays when you don’t have to; you take the low-risk high-reward route. Because of this, Blizz reworked him to force more engaging play. For lower SR Lucio players it didn’t make a huge world of difference, but it let higher SR Lucio players really pop off with the hero and take him in a whole new direction.
This is exactly the treatment Mercy needs right now. She, just like Lucio then, is fine when viewed in a vacuum. But you have to look at hero synergies and the risk-reward ratio of a hero for balance as well.