To me, premier means that they're one of the best in the league at what they do. Hardy is good, no doubt about that. Last year he was top 15 in sacks, not top 5.
Sacks aren't the only thing a DE does. The most important, but not the only. If you were to factor in QB pressures, run stops, TFL, forced fumbles I bet he'd be a top 10. Haven't crunched any numbers myself, but a number of the guys who had more sacks than him were strictly pass rushers, not the total package.
Plus, how many ahead of him in the sack list were 3-4 players?
edit: I just looked it up, only six 4-3 DEs had more sacks than Hardy, and one of them was CJ who had the most of them all.