Agreed. They need to filter the voice through a modulator. It adds some authenticity as well since someone such as Bruce would employ one.
Bale's Batman voice in Begins was the best out of his three films. I don't know what the hell possessed him when he was doing TDK, though. That one was absolutely shocking. He sorted turned it around for TDKR, but it was nowhere near Begins. At least to my ears, anyway.