Well, Assassin is my favourite class but ever since a short a while ago a bug has made then hard to play. The Assassin's attack is delayed for a relatively long time, and pretty much all the skills (grapple, cloak, smoke bomb, attack etc.) are delayed once the button is pressed on the controller (movement not inlcuded). This issue has only been happening recently and i do not have this problem with any other classes. Also when making an Assassin custom class all abilities are delayed too. Uber, please fix this.
I am pretty sure that nothing has been changed in the past day of me not playing. I believe that your issue is lag related and not system related unless there was an update that I do not know about. However, there IS a delay on the smoke bomb and the cloak which is intended for balancing issues. Try playing on a local Blitz match and see if your commands are still as delayed as before, I have reason to believe that they are not.