Provoke does nothing when you're on top of agro list. It's only used when you want to get on even ground with someone else that's top of the list.
All in all it's a bit lackluster now as the +1 agro it gives over the top is pretty much nothing. They should have went with making you a forced target for X seconds along with equaling out your threat, that would give you some time to build up on it.