The bottom line is......
There's no way in the world you could get any #1 draft pick for Spears or Carpenter, not even a late first round pick.
That doesn't make either of them "busts" nor does it mean either "sucks."
However, they were unfortunate selections by the Cowboys.
No one would give even a #32 pick for Spears as a DE because he can't rush the passer at all, which means he would be a total flop at 4-3 DE. He also has never proven to be tough enough to play 4-3 DT. He is a run-stuffing DE who doesn't get any pressure on the QB and who doesn't get into the backfield for tackles for loss, either. He can have a long career in the NFL as a 3-4 DE, but he is not worthy of the selection used on him, and it remains to be seen whether he can remain a starter.
Carpenter has some pretty good LB's in front of him in Dallas. My guess is that he could start for some teams as a 4-3 OLB. However, even though he still has time to develop, he's clearly not a stud LB...he will also end up somewhere when his contract with Dallas is up, but there's no way any team in the NFL would give a #1 selection for him.
When you spend two #1's on guys where we selected Spears and Carpenter, barring injury, you should be able to look around and see plenty of teams that would give you a #1 pick for them. Right now, Spencer would garner a higher selection than either of them.
They were not good selections for the Cowboys...period.