Oh there have been mimes as villains before, Le Mime from Xiaolin Showdown , but jokes aside he was used as well as a way of comedic relief, so that is something they did manage to do differently here.Mimes aren't particularly known for being villains.
As for the episode it was really light on being assertive towards the wrong doing that occurred really it felt more or less unjust to what happened and the resolution not so great but somehow I felt the episode was somewhat enjoyable, action mainly being the case I guess.