Fleury/Faulk was one of the Canes most common defensive pairings last year. The most common pairings for Carolina last year were:
Slavin-Pesce
Fleury-Faulk
Hanifin-TVR (the most sheltered pair).
Fleury was a -2 and Faulk was a -26. Hanifin / Faulk would be a much worse idea.
According to DobberHockey:
Haydn Fleury’s most common linemates:
Fleury-Faulk = 47.14%
Fleury-TVR = 24.98%
Faulk’s most common linemates:
Fleury-Faulk = 34.32%
Slavin-Faulk = 24.3%
Hanifin-Faulk = 20.38%
As you say though, the real issue with the Canes is that Faulk and Hanifin are both offensive top-4 D but they are a disaster playing together. Which forces the Canes to either 1) Break up Slavin-Pesce or 2) Throw Fleury to the wolves. They tried both with limited success.
I think the Canes defense would come a long way just replacing one of Faulk/Hanifin with a guy like De Haan or Hjalmarsson. More likely than not either Faulk will go or Fleury will go and Hanifin will continue to be sheltered on the 3rd pair.