The main Reason why Her Kit Is Bad is because
1st Her Nade that forces opponents to crouch is one of the most dogshit ability in the game. Crouching Increases accuracy and The tag is easy to remove.
2nd like the trips doesn't hold flank like other Sentinal but trips can be used to Hold site as The stun is quite nice.
3rdly The barrier she puts up is also one of the most useless Ability in the game. Barrier Type agent were never in meta I mean Even sage had like only 1 game at champs and sage's barrier orb is way better. Deadlock's barrier only blocks Movement but u can still kill someone through it . Also Her just doesn't make sense to a True Sentinal.
Deadlock is a Dead agent I don't see any buff making her way in the meta .