I have a few thoughts on new abilities for future heroes that could be anti-mobility. These are rough drafts, so take appropriate salt.
Super Adhesive
Spray a sticky substance in a cone that significantly slows enemies, prevents them from jumping, and prevents them from using mobility-type abilities (i.e. Blink, Guardian Angel, Cyber Agility, etc).
This one’s relatively like Sombra’s Hack, but doesn’t stop the enemy from using stuff like Fire Strike, healing allies, etc. It just stops them from dashing around and makes them much slower.
Shackle
Fire a skillshot that latches onto the first enemy it hits for X seconds. While latched, your enemy cannot move more than Y-meters away from you, or they will be forcibly pulled toward you.
This one’s inspired by Maiev in HotS, and keeps an enemy from fleeing or putting some distance from you. This one would be on a Lawful type of character who seeks to put Overwatch and Talon away.
Shock Charge
Plant a mine (akin to Widowmaker’s Venom Mine) that inflicts a slow on the enemy that triggers it.
This one’s better on any other snipers we get, preferably one that has a long charge-up on its shot (i.e. the weapon should function like a Spartan Laser). Not only can it slow the target for an easier shot, it’d also let you know if someone’s flanking you if you use it for such.
Feel free to suggest your own ideas.