According to my owners manual (2016 NC750x) idle should be 1200 +/- 100 rpm, but if your RPM is (really) higher than normal the clutch will engage and the bike will creep. So to me if the idle speed is high that's the problem, not the DCT.
From the service manual for high idle check-
Intake air leak, clogged air filter or engine top-end problem
Throttle operation and freeplay
IACV operation ( idle air control valve)