Considering that 99% of online matches in Brawl include items ( being thrown all about making it impossible to avoid damage for that long of a period of time), it wouldn't be that useful then either, unless the general mindset changes and more people neglect items. You might trick someone for 2-3 seconds until someone massacres you in the face with a thrown beam sword or something. It would be rather pointless really.Thats why its a gimmick. It would help in some situations, and hurt in others. Imagine the mind games in a 4 player online match for those who arent expecting it or paying much attention.
For it to work, Zoroark would need a special move that allows him to take the opponents form and use it's a/b moves until hit or until a certain period of time passes.