Recruiting rankings are an in-exact science for sure.
I enjoy following recruiting as much as time allows. My approach has always been to look at it in terms of probabilities - the higher the ranking, the higher percent-chance of success, but it's far from a guarantee.
The one important trait that's not factored in is character. The Iowa staff has been known for years as a staff that will not sacrifice character for flash, and for the most part it has showed. They've still had their misses, but in that area they have succeeded for the most part.
Where the program gets hurt is when the high-character guys that need developing get forced into action prematurely, so the team disproportionately suffers when successful players declare early. We are not a reload program and never will be.
Getting back to the o-line, in fairness losing Wirfs and Linderbaum early hurt, along with losing Davidkof, Britt, Jeff Jenkins and Tyler Elsbury to transfer/retirement, but we've brought in enough recruiting talent to have at least a decent line. The current performance issues, particularly the lack of basic fundamentals, fall back on coaching.