I have a 2015 MS with about 21,000 miles on it now, bought new in 2014.
It has several RPM ranges that are smooth and several that are a bit buzzy, with almost all of the vibration felt in the handlebars. I installed Grip Puppies right awa, though mostly because I like a fatter grip. The Grip Puppies were the single most effective thing I've found for reducing vibration. The engine did feel smoother after the 18,000 mile service, but there are still buzzy ranges.
I've had a number of big four cylinder bikes over the years - 1975 Kawasaki Z1, two K100RS's, a 550 Suzuki, and 3 weeks on a rental Yamaha 1200 in Europe. All of them had similar vibrations and ranges. I just try keep the RPMs in a smooth range.
I also have a Kaoko throttle control, but I don't like it. I did not notice any change in the vibration level, but the angular ridges on the control feel uncomfortable against my right hand. It turns out I don't use it much either. The bike has so much power that speed varies too much with a simple throttle control (like down hills versus up).