Bustability pretty much happens at every position with a first round selection.
But for comfort I will point out there have been many successful 1st round DTs in recent years (it even used to be a habit for Belichick in New England when he first turned his club into a winner)...
Dontari Poe - too early to tell but with 16 starts he doesnt seem like he is a bust just yet.
Marcell Dareus
Phil Taylor
Ndamukong Suh
B.J. Raji
Haloti Ngata
Vince Wilfork
Tommie Harris
Ty Warren
And there are tons of solid 1st round DEs...
Bruce Irvin
Chandler Jones
Aldon Smith
J.J. Watt
Robert Quinn
Cameron Jordan
Jason Pierre-Paul
Chris Long
Mario Williams
Mathias Kiwanuka
Demarcus Ware
Marcus Spears
Will Smith