It's not the same thing. Actors can't change their appearance, http://www.youtube.com/watch?v=vuaD6cC5RpA.
Yes, but it's ridiculous to ask a voice actor to change voices for two completely different characters in two completely unrelated games.
Edit: Also, in the piece you posted, the (very talented) actress is basically using dialects to change up her voice between characters, with the only exception being when she uses a cartoon voice to go to an extreme. Unless you wanted Tullius to sound foreign (which is silly, since he was supposed to fit in with the Imperial dialect that was established), he was going to stay with his normal voice.