Mustard and I think the Deathstroke-Bane matchup is a 5-5.
Due to the dash buff, Deathstroke can only keep Bane out for so long until he inevitably gets in, and the armor properties of banes venom specials stop deathstroke from being able to wakeup with sword spin, meaning the wakeup option out of Banes pressure becomes a huge gamble given you must wakeup with a heavily unsafe sword flip. spin is straight up not an option in the corner, but you can occasionally escape with it midscreen. Meaning neither character has the edge on Deathstrokes knockdown.
J3 when Bane is venomed is also easy to stuff due to venom upper. Deathstroke has to rely on hitting bane when he either has no Venom, or is debuffed. Should the bane player manage his Venom correctly, it becomes very hard for Deathstroke to play his main game.
That said, When bane IS debuffed, gunshots always work a treat, and if you can end your combo in focus right as banes venom is about to run out, you can cause serious unavoidable damage. Not to mention you can still zone bane to an extent. Definitely a character I feel you have to try and keep off you.