Because it seems like most low-tier players are either the casual type or completely new to FPS/this game's mechanics. Therefore when she requires the skill check, she wins the skill check.
Then you have the mountain of lies and meta slaves that believe that 76/McCree are the ONLY one able to counter her, when it's just nor true.
A Zen + Winston can make them panic since if they aren't careful they could die.
Dva is a passive counter, who can soak her damage.
Bunker Bastion is another strat (in combo with Zen for ez butter cutting).
Or as creative as Torb distracting her with a turret.
But that's just Pharah. When Mercy is added, a lot of leeway is given to the Pharah player (I would know with my 40-some odd hours on her). She is allowed to be more aggressive and soak up damage because Mercy is effectively increasing her health pool (which kinda works like how Tech Hank's shields act as a damage reducer, but with Mercy she is giving Pharah more health).
That then Mercy's damage boost means Pharah players can kill enemies in 2-3 splash hits, whereas Pharah alone needs to land direct hits in order to be successful and win fights.
SO all of this in total, combining a higher HP hero (due to mercy healing) and more damage output (allows for more leeway in dishing damage) causes an imbalance, where Pharah has the advantage in the fight and the enemy does not.
But once again, it comes down to the skill check, aim skill check in the case of Mercy, and teamwork skill check for taking down Pharmercy.
This is why Mercy needs a little clip on her wings. She enables Pharah, a balanced hero, to be better, while in turn keeping a safe distance to those who counter her.
That's why I suggest putting a resource meter on her passive float, so she can't hover/fall endlessly, and it only regens while she is on the ground. It doesn't completely break Pharmercy, but it makes it more clunky to use, and especially not effecting them outside of the synergy (because how often is her float used over GA? Not very much).
This is the best option I see atm because if you start decreasing Pharah's damage, she will either require Mercy much more cuz damage boost make up for the damage nerf, or if Pharah's jetpack gets nerfed she will be useless half the time in battle because of needing to land, essentially pushing her back into F tier like she was months after launch before her November buff.
Plus there really isn't a reason to nerf them outside of Pharmercy. Unless Mercy gets a complete overhaul, which I wouldn't be for nor against.
Ninja'd by @SedoUmbra
I'm around 3000SR since I blew this season over by maining defense heros until I stopped playing recently.
A few times I'll jump back on, and mostly when people ask me.
Es mi profile & stats.