I think some of this too has to do with talent. BP inherited a better group of kids than MR has by far. Interestingly enough, Bo's best defenses were those early groups and I think a lot of that had to do with talent. His staff wasn't consistent in doing a lot with a little (like a Bill Snyder at KState, for example).
I'm not sure it's "by far". I think the defensive talent gets a lot of talk - and deservedly so - but there wasn't a whole lot there on offense.
It's tough to know what to use to judge talent level but looking at the NFL draft should give a decent idea. In the three year after Callahan left there were three Huskers drafted in 2009, three in 2010 and seven in 2011. However, one of the of the 2011 guys was a JUCO (Gomes) recruited by Pelini. So that's 12 guys drafted in three years but only Helu and Paul were offensive skill players. There were three OL but only Slauson ended up doing much.
I'd say Carter, Valentine, Collins, Gerry and DPE are basically locks to be drafted. And I'd put Lewis, Davie, T. Newby, Westerkamp, Banderas, Rose-Ivey and Alexander as having a decent shot along with another WR and possibly OL depending on who emerges. If those five get drafted, along with 4 out of those seven plus a couple more, that's pretty much on par with what Pelini started with. There might not be that many but I don't think it's out of the question.