He was on an awful defense and got cut? What makes you think he wasn't part of the problem?
He got released because he was overpaid and the new management preferred to cut their losses after the 2-14 season, they basically cleaned house of all the over paid players just eating up cap. That doesn't mean Ross wasn't a good player, just means he wasn't worth 5 mil a year, it was a bad contract to begin with.
Playing with a bad front 7 is the worst thing that can happen to a cb, hard to look like an effective corner when your just chasing shadows all game because your pass rush isn't getting any pressure. Eventually it starts to kill your morale when your job becomes exponentially harder because of the lack of pass rush.. It's hard to feel good about yourself and be on top of your game when your just demoralized from playing on the worst team in the NFL.
Ross has A LOT to prove in camp if he wants to make this roster but it's not fair to call him mediocre, been a victim of circumstance to a large extent with the Jags stint and the injury last year.