I can't recall if it was the Packer game earlier this year or some other game...Hester let 3 punts bounce and they replaced him on the next punt, evidently to send a message, because they sent Hester back out on the next punt. It was a bit shocking, and a tell that his best days are behind him.
Anyhow, comparing Hester/Cobb really isn't a comparison, is it? Hester's a kick returner who happens to get thrown some balls from time to time. Cobb is a receiver, who happens to return kicks, and his days as a returner are probably numbered. He's become too valuable as an offensive weapon to risk injury. I'd look for a speed WR/return guy in the next draft who wants to make his bones (and risk his bones in the process). At some point Cobb is going to start making business decisions on these kicks, if he hasn't already.