Mithrandir said:
... Make him remain silent for a more Vaderish attitude.
Well, that's the thing.
Hayden ain't that bad of an actor, it's the dialogue that makes him seem like an idiot. Bob's version of The Opera Scene proved that when you remove some of his lines and make him a bit more silent - he says a lot more with his body language and facial expressions.
That's what I think, anyway...