I didn't think Bale underperformed at all. If I had to pick the underperformer, it was probably Maggie Gyllenhaal. I wouldn't say its her fault, as I don't think Rachel was a very good character. She was better than better than Katie Holmes, but then again, that was expected.
I'm sorry, but Bale as super raspy smokers voice Batman annoyed the hell out of me.
"You hear that? *cough... cough... cough* That's this city.... *GAEEAGGGHHHH!* Sorry hairball... this city showing you what kind of people live here"
Yeah, I butchered the quote, but that's what I thought was going to happen during "Batman Talk" time.