So you're holding Mo (after 2 seasons in the NFL) to the same level of expectation as a 4-year vet (Tyron) and a 5-year vet (Dez)? That alone destroys the credibility of your post.
What's more incredulous is that you think Dez and Tyron "dominated" anything their rookie seasons. Both were solid contributors (Dez had 45 catches for 561 yards and 6 TDs), and we could tell they would be special once they (and their game) matured. But if you think Dez was dominant (not dominate - it's a verb), then you must have Terrence Williams in the Hall of Fame already. In his rookie season, he had one catch less than Dez (44), for 736 yards and 5 TDs.
Mo, like all of DBs, have labored under the misfortune of playing behind a non-existent pass rush. There not a CB in football that won't get abused if he has to cover for 7 + seconds. This is his 3rd year in the league - the year most players finally "get it". Let's see if he can stay healthy before we flush him off to glory. In the end, it will be his durability, and not his ability, that does him in.