Didn't Doffy defeat Law in the same fashion? Both of these fights were off-paneled! On top of that Smoker had just let himself get beat to sh*t by Vergo to get Laws heart back. He wasn't exactly in a good state when Doflamingo arrived.
The VA's in the New World also work in Paradise. VA's are VA's. Va's will be stronger after the timeskip as well as weaker. But you can't say Smoker is weak since he's pretty boss, strangled Law in second, so if it wasn't for his warping (which was clearly an asspull by Oda to save him) then Smoker would've won the fight quickly.