You don't measure a guy like Vaughn with his PPG because his role isn't to score. His role is to run the offense smoothly and facilitate the ball moving through TD or Manu as well as doing his part in smooth ball rotation to open shooters. His job is also to play defense and be tenacious. He does all of those things well, and in addition is a locker room and floor leader. I thought he played well during the PO and did everything a backup PG is supposed to do.
That said, I would like to get a bigger PG to supplant Beno, mainly for matchup reasons. Since TP and Vaughn are both small, a bigger PG could be useful in matchups against guys like Deron Williams.