I don't know either with Pollard. I just know that a lot of players have trouble judging punts, then with the footsteps that are near them while fielding the ball.
I don't see Dallas having any problem letting Cobb handle the Beasley role. Beasley only returned 11 punts last year. He was mainly back there for sure hands, with 18 fair catches. Cobb does have some fumbles in his punt return history, but I would think the team would trust his hands more than a rookie or first-year player who hasn't shown his reliability yet. (I don't know with Cobb if his fumbles came while fielding the ball or during the return. He has nine in 156 opportunities. Austin has 17 in 241. So their rates aren't very far apart — every 17 punts fielded for Cobb, every 14 for Austin. Five of Cobb's fumbles came his first two years, though, but he also received a lot more of his opportunities then.)