The kid is still 22. He played very well as a rookie RT. He started out rough at LT last year, but got much better as the season went along. The line for the most part was crap. He was arguably the lone bright spot. He also didn't get much help last year either. New position, new OL coach, new schemes. He'll be fine.
As for whether we should have taken him or JJ Watt, well that's really a futile exercise. You can go back in hindsight, and come up with enough players who should have been taken, to fill a stadium. That's for any team, not just the Cowboys. I wish we would have taken Watt, but the reality is, we didn't. Making myself miserable over coulda, woulda, shoulda is just pointless. And yes, Watt is the better player now. Doesn't mean he will be in two years. A lot of people were going nuts after Merriman's first two years, saying we should have taken him over Ware. Nobody saying that now.
And as I alluded to earlier, as good as Watt has been, he hasn't helped Houston win a thing.