But the brutal thing is that we dont have a reliable counter to mobility in this game and its a serious problem.
Mei would be the most reliable at that job. The point is you should be having a hard time trying to escape Mei. Maybe reduce her range to make up for the fact that it locks out mobility abilities.
The only people she counters now are the heroes with no mobility. It seems super pointless.
At the very least, her ult should act just like Zarya ult and lock people out of movement abilities.