The Dragons, who have flattered to deceive in recent seasons, looked well placed at half time but fell away in the second half as the reigning champions ran in five tries.
Eli Walker, Ryan Jones, Gareth Baker, Mike Sully and Bowdy Davies helped themselves to tries with Tom Priday weighing in with five conversions.
The Dragons scored twice in the first half through wings Neil Jenkins and Luke Davies but the two unconverted efforts proved to be scant consolation.
