This is an interesting point that isn't brought up very much when people talk about recruiting. I definitely believe that offensive performance overrides defensive performance in a lot of draft boards for two reasons. First, it is much easier to notice offensive performance through statistics and direct observation. Second, scouts are very interested in getting players with untapped potential, so that often leads to a preference for athletic players rather than experienced players who have already developed multiple aspects of their game.
As for its effect on recruiting, I'm not sure. It is definitely a feasible theory, but a lot of the guys who were targeted by Duke (especially Patterson, Echenique from what I have seen, and Monroe) are very good defenders who would have no problem fitting into the Duke system so I don't think they would be intimidated by K's emphasis on defense.
As for Knight, I think that the only reason why he didn't have as much interest in Duke as many expected is because of Irving's vocal interest in Duke.