That seems reasonable.
That is what the Mercy players are saying though, how much value they get from their abilities is a lot more out of their hands.
Boost heavily relies on the person you are boosting. You will never do a lot of damage with it, it is there to lower TTK, and just win that tiny window when burst wrecks the enemy.
Their healing is also very much dependent on the person they are healing, and to a VERY large degree on their position, and the enemies position. Your positioning is far less of a thing. A widow shoots your healing target in the head, and it doesn’t matter if you were in the combat or not really. Rez is literally the only answer you have, and people hate it.
Mercy is a “slightly tilt the battlefield” hero, but, like it is a very gentle tilt over a long time (like, many many many games long time) - and I can see how people can say from a balance point of view that is ok, but it really sucks from a player point of view.
Your SR just drifts around with a slight push towards where it should be. The biggest thing you can do as a Mercy player is play conservatively, where you don’t do anything particularly well, but you don’t do, anything horribly, and team up with people who have a much higher SR than you do.
And abuse the fact you have so little direct influence on the game, that acting as a way for them to play against lower ranked players is the biggest influence you are going to have. I’ve done this as a test, and got WAY out of where I should be rank wise doing that.
That the most influence you are likely to have is punking the matchmaker because you have so little impact, is a truely sorry state for a hero.
Like there shouldn’t be a climbing strategy for a hero involving “have no impact one way or the other on the games you play”