They are scheduling weak non-conference opponents while they are rebuilding their program for the same reason everyone else does....to try to win at least 6 games so they can go to some dipshit, meaningless bowl game and be able to tell recruits that they went to "bowls" in 4 straight years, or some such nonsense.
And while it is probably cyclical, Duke's division in the ACC is definitely weaker than WF's division right now....as other posters have noted. That helps Duke's record, too.
Personally, I wish they would do away with that meaningless 12th game against all the Presbyterians in the country and go to a 16-team playoff. If they did that, only 4 teams would end up playing more than the 13 games they are playing if they go to a bowl now. (And two of those 4 teams will be playing 14 games now, with a 4-team playoff & a 12-game schedule. Actually 15, counting a conference championship playoff game.)
And by the way, I know this was a long, long, long time ago and really doesn't mean squat right now, but I'd venture to say that almost none of the posters on this board have much of an idea about just how much tradition Duke had in football for a very long time. For the 28-year period from 1930 thru 1957, Duke had a winning record in football every year except 1946, when they went 4-5.
As I said, that's pretty much ancient history.....but still, a winning record in 27 out of 28 years shows there is a helluva tradition there, if Duke ever decided that they wanted to get serious about football again.