It didnt take luck to produce a draft like the one in 2005. It takes a firm understanding of the kind of defense you want and drafting the right players that specifically fits your scheme.
Parcell's specific scheme called for a traditional 3-4 defense. That means big run stopping DE's that behaved more like DT's in a 4-3. It meant a big wide bodied NT and lots of athletic fast LB's.
DE's in his scheme were not notable pass rushers, their job, along with the NT was to clog up the line of scrummage for the LB's who always got the big numbers. His 3-4 DE's were always the unsung guys but they played a key part in their success. Their stats were a useless method to evaluate their performance.
Parcels would have preferred Ratliff at DE, he got Jason Ferguson in free agency to be his NT.
The key to pressuring the QB in Paecell'a defense was the element of surprise, you never knew who the 4th and/or 5th pass rusher was going to be. He or they could come from anywhere. It wasn't unusual for every single defensive starter to record a sack through an entire season.
This is why Parcells didn't place as high a value on Ware, who lacked the natural instincts of multi tasking linebacker. Indeed, Ware often had issues in the running game, often taking himself out of a play with aggressive reaction to play action.
The problem after Parcells left was that Wade Phillips 4-3 was completely different, he wanted more aggressive pass rushers in the Deline and needed smaller more agile DE's. So Canty and Spears lost value.
Ratliff stayed at NT so the whole line got quicker but smaller. Ware became the designated pass rusher for all practical purposes.
On the surface, it looked as though it would work but there were issues that eventually destroyed them.
They could be dominates by a power running game and that was the fashion in the NFC east.Guys like Brandon Jacobs and Clinton Portia ran up big numbers. The defense would get fatigued and eventually cave.
Opponent offenses correctly assumed most of the time that Ware would be the other paas rusher so this 3-4 defense quickly evolved into a 4-3 defense out of position.
The moral of the story mirrors my opening statement. A particular strength or ability is only valuable if it is an element of the type of defense you are building.
Don't get talented players on the D-line, get the right players with the right attributes for their style of play.
But do the Cowboys have a vision for the type of defense they want to be? Do they even know they are supposed to have a vision?