I remember way back when it was announced Symmetra would receive a second rework, one of the things I suggested was that if an enemy was being hit by 3+ turrets at the same time, it should lock off their movement abilities. Like Graviton Surge do. This would prevent high mobility heroes from simply escaping the turret ranges, and serve her purpose as a mobility counter. It would also provide some interesting interactions, like stopping a red Rein charge if he goes through a warded gate.
Then Sym3 arrives as a completely new character (mechanically speaking), and this buff would be too strong when you can throw turrets from afar.
IMO, builders in general should be strong at countering high mobility threats. It’s how things should work: Bulky tanky types are easy prey from enemies that can outrange them, fast nimble types are easily shutdown from enemies that can prepare in advance, and static defensive types should be countered with raw damage and resilience.
Torb is still good against mobility heroes (although the new Molten Core is stronger against tank types), but current Sym got in that weird spot where she don’t have enough damage to fight tank types, nor the countermeasures that would allow her to stop mobile heroes on their tracks.
Sym was build originally to be a support character. As such, her whole concept revolves around empowering her team instead of dirtying her own hands. When they moved her to DPS, it clashed with her original design, and now she can’t do enough damage or supporting.
IMO, Blizzard should come back to their original stance that support do not mean healer, and move Sym and Sombra into support. Because that’s what they do best, work as the “third DPS” of the team, and creating opportunities for their teammates to engage (Sombra) or not be engaged (Sym).