Hubert has greatly improved the effort, intensity of individual players on the defensive end. Roy talked about lack of effort, want to, etc regularly his last few seasons. Hubert for the most part has solved that effort issue. On ball defense is the individual's attempt and success/failure is measurable/visible. In general, our on ball defense is winning defense. But the moment you merely introduce a simple screen/roll, it falls apart(the Wake game was a constant display of failed defense resulting in open shots).
JMO, the problems with team defense is the same issues with the team offense. It is a lack of system. Hubert has failed to implement a complete offensive or defensive system. He has installed sets that contain ideas/principles. This is rather hard to understand since Hubert played for Dean(an ultimate system coach) and tutored under Roy (who had patterned offensive system). The reoccurring visual failure of offense/defense can only be solved by a system. Unless Hubert gets some intervention implementing a system before next season, Carolina will fail to maximize its talent.