What are you looking to do with the action?
I replaced the Defiance on my PRS rig with a Mausingfield and couldn't be happier. Too tight of tolerances on my Defiance, and the cerakote certainly didn't help. In all fairness it was an older Defiance - a Rebel/Gap Templar V1, so probably not fair to compare to the new Defiance Deviant actions, though I've seen people with Deviants struggle in conditions due to the tight tolerances where actions such as the Surgeons, etc. kept chugging along with no issues.
@Terry Cross builds his field guns on Defiance Deviants and has good luck with them, but I'm not sure if he is ordering them to a different spec than what is offered off the shelf.