I agree with you. If the Cowboys didn't have so many holes, it would be tempting to move up, but as it is, there are just too many holes.
But having said that, it would have made more sense for the Cowboys to move up to fill a clear position of need with a top-flight prospect (e.g., Warmack) this year, than it did last year to move up for Claiborne (after signing Carr) and crippling the team's ability to use a high choice on a greater position of need.
Claiborne cost more than "peanuts." He cost the Cowboys resources that could have been allocated to greater effect. As it is, the team finished 8-8 and out of the playoffs again. In the short term, anyway, the Claiborne move wasn't particularly effective.
Ironically, allocating significant resources to Claiborne last year means it is less viable this year for the Cowboys to allocate a similar amount of resources this year to fill a position of greater need with a top-flight prospect.