The vibration when decelerating from 3000-2000 RPM is inherent in the design for whatever reason. It is normal. You can easily counteract the annoying "chatter" by up-shifting, down-shifting or just going into neutral, depending on the situation. I've had mine for just shy of a year and encounter it all the time but am used to it. Almost 20,000 miles on my manual and no problems yet.
As for drone in 6th gear, I'd say that's not normal. The only time mine had ever given me any drone was when I pulled the mufflers off for a few weeks. It nearly drove me crazy, so I put them back on. If you are getting drone from the factory setup, I'd recommend having your exhaust system checked for fitment. Perhaps something wasn't assembled quite right? But then you'd think there'd be some other exhaust noise?
Are you sure you're not getting some other kind of weird vibration that's coming across like a low drone?