I took a look at how Duke is performing relative to expectations and relative to opponent strength in ACC play. Games that were early in the season are not going to be as useful to look at, since Vegas expectations are based less on actual performance at that point; the beginning of the ACC schedule seemed like a nice cutoff for this.
Boston College (#125 Kenpom currently): +0.5 (beat spread by 0.5 points)
@Wake Forest (#115): -7.0
@NC State (#59): -21.5
Miami (#63): -31.0
@Louisville (#10): +14.5
Pittsburgh (#95): 0.0
@St. John's (#40): +2.0
@Notre Dame (#17): -5.5
@Virginia (#2): +11.5
Georgia Tech (#75): -11.0
Notre Dame (#17): +21.0
@Florida State (#124): -8.0
Duke is 4-1-0 against the spread against top 50 teams in ACC play, with an average performance of +8.7 points relative to the spread.
Duke is 1-5-1 against the spread against sub-50 teams in ACC play, with an average performance of -11.1 points relative to the spread.
There is only one team between #17 and #59 in this sample, and the result against #40 was close to the spread, so we could look at top/sub-17 or top/sub-25 or top/sub-59 and everything in between, and it would tell pretty much the same story of a team that has recently been basing its effort level, focus and preparation on the strength of the opponent.
Duke's remaining games are @#78, vs #12, vs #85, @#160, vs #78, vs #115 and @#12. I would expect two more good performances the rest of the way, both against North Carolina.
It seems Duke's biggest hurdles will be winning their first game in the ACC Tournament and their first two games in the NCAA Tournament. If Duke ever plays Kentucky, I would expect Duke to blow out Kentucky, but I do not expect Duke to make it past the second round of the NCAA Tournament.
During those seasons when Duke seemed to play at the same level almost every game and never lost too badly, most Duke fans wished they had a team that could find another gear for the biggest games, like Florida 2008 and UNC 2009. We have that team this season. Unfortunately, we also have Jahlil Okafor.