Dallas isn't the right team for him unless they were to change their defense to suit him. Hall can be a very good zone cover guy, but he proved in Oakland that he couldn't do man coverage if his life depended on it. Dallas likes to leave their CBs in man coverage a lot, so Dallas would be a horrible destination for Hall.
If you want the Hall who was occasionally brilliant in Atlanta instead of the Hall who looked awful even compared to the rest of the Raiders (!!!), you need your team to play zone pretty much exclusively.