It's disingenuous to over-reach and say "2 for 10 in the last two drafts" when I've actually named FIVE starters on this very roster (Crawford, Williams, Murray, Harris, Leary) alone.
Remember, we're talking about potential. No team in the NFL hits on surefire starters in the first three rounds without fail every single year that they require fresh starters. You know that, I know that. If Crawford is a sure fire starter, like you say, and so is Ware and so is Spencer if he returns, and so is Nick Hayden if he stays (he started all year), then what else do you need?
Lets suppose for a moment that you toss out Hayden and add Rookie Tackle as the new guy. You still have Hayden potentially in rotation along with a returning Ben Bass, and a player like Jairus Wynn who stuck around on the roster despite the churn. You're also going to add more guys to compete in camp through the draft as well as UDFAs.
This Cowboys defense is not going to become the Seattle Seahawks in one draft. Having that as an expectation is ridiculous, just like all of the other absurd expectations of the hand-wringers on this website. ESPECIALLY when Seattle didn't do it in one year (it took them three, actually).
Regardless of what our fans want to try and believe, this defense is not one draft away from competing. It's a work in progress, and reloading certain positions on the offense (like the Escobar pick last year) are equally as important as continuing the defensive build.