Symmetra has been stealth nerfed multiples times

[Tobsi-21949]

No but it was confirmed by one of the developers.

These patch notes

Hey there! Armor used to have a varying effect on damage over time and beam type weapons based on how damage instances were handled by the server (it’s not the server tick rate, some weapons have different update rates). This meant that Winston’s primary fire would hit the maximum 50% damage reduction against armor because it had a faster damage update rate while Zarya’s beam would lose a flat 15 damage per second (after the armor change from -5 damage per hit to -3). So the general results …