The Xbox controller isn't properly optimized for fighting games, but instead, is tailored for gaming genres such as Racing games and Shooting games with its shoulder triggers and analog placement. Granted I still like playing Xbox with friends, its not meant for fighting games...or at least not without a stick.
Outside of DOA5 Vanilla-LR, the only DOA game I've played on Xbox was DOA4, and I sucked literal ass in DOA4! I couldn't get used to the controls, or the controller for that matter. I figured I might as well give up and then all of a sudden, DOA5U Core Fighters on PS3!