There's a pretty big middle ground on 4th round picks in general. There was a stat floating around pre-draft - I've got the whole thing saved somewhere if I can find it - that gave the percentages of draftees, by round, who are still with the team that drafted them by the end of their rookie contract.
For 4th rounders, it was 25%. Let that sink in. That's not 4th rounders that became starters. That's 4th rounders that just are still on the team at the end of their fourth year in the league. So 75% of all 4th rounders are gone from the team that drafted them by then.
This isn't really directed to Hitchens as much as it is to fan expectations. I'd love it if Hitchens is a quality starter. Same for every Cowboys 5th round pick, 6th round, etc. But to have the expectation that a 4th rounder should be a starter...the recent history of the league, not just the Cowboys, doesn't bear that out.
It'd be nice if 4th rounders all turned into Richard Shermans. When you hit on one and he is a valuable starter, that's great. But the odds are working against you by the time you get to day three. I think that's why you see a lot of teams - not just the Cowboys - start taking flyers at around that stage in the draft.
As for Hitchens, I have no idea how he'll pan out. But if your scouts have someone rated as a 4th rounder, and the draft gurus have him much lower, how silly could it possibly be to not take him because Kiper/McShayet al didn't agree with you? You take your guy unless YOU'RE confident you can get him much lower, then you get proved wrong or right on the field, not in preseason of his rookie year.