Tumble (Q) has many uses, but it cannot pass over walls.
Condemn (E) can be used to both pin targets to walls to ensure kills, or to escape.
Don't go in first on large teamfights. Wait for your team to initiate.

Playing Against Vayne

Vayne is fragile - turn up the pressure on her and she will be forced to play cautiously.
Deny Vayne the opportunity to Condemn pin you against walls.