Was watching some streamer the other day trying to pull off Black Widow in Celestial. Every time he picked her at least one of his teammates lost their shit, wishing death upon his family etc. He was doing relatively fine, winning a bunch of 1v1s against Black Panther and Spiderman but overall she's just...so lacking compared to any other DPS. You focus on a target for 1 second too long and you die. You revisit the same angle too early and you die. Best case scenario is you hit a bunch of headshots but it accomplishes nothing because your team can't follow up immediately. I had a lot of fun with her but hitting headshots often feels like tickling the enemy team, and not hitting headshots feels like throwing.
Idk what kind of buff would make her viable, especially in higher levels of play. The oneshot headshot would probably be too aids, but maybe increase her firing speed, give her something like charged shot that oneshots occasionally like Hawkeye or something.