Placebo Effect, Placebo Effect, Placebo Effect.
(Yea I said it 3 times)
No it's not. Official 1.14 fix, although VERY minor and pretty much unnoticeable.
I didn't play against it too much after the nerf but those that did blindfired it which still kills insanely quick, and when I used it I also had on an item that increased stopping power but cut RoF by 5% and yet with that and the nerf it still was definitely a lot faster than the regular M9.
Hopefully it didn't update properly and it will be re-patched ASAP.