I dont know as much as many here, but ive seen it stated (and it makes sense) that big NT/0-tech DTs should not be drafted in the first round, especially early in the first.
The reasoning is that teams spend ~70% of downs in nickel or some other pass defense set up. Your big run stopping DT would normally be on the bench for most of those plays.
The reasoning seems sound to me that any player you draft that early, especially top 10, should be a player you expect to be on the field for almost all the snaps.
Also have read that most good NFL big run stopping DTs are usually available on day two and sometimes early day three in deeper drafts.