I'm new to Cyclefish but have owned my 2012 Switchback for a little over a year and have about 7,000 miles on it.
Nearly every Switchback I've read about which has the stock exhaust system vibrates badly from about 2,700 RPM to 3,200 RPM. Mine did as well. This is specific to the Switchback and not the Dyna line in general. Why? The Switchback is the only bike in the line with this muffler and associated mounting/support bracket. The bracket is not used with aftermarket exhaust systems so if the exhaust is changed the vibration goes away.
On the bottom side of the muffler near the middle there is a bolt that attaches the muffler to the center of the support bracket. Temporarily remove this bolt completely. Start the bike. Run the engine tp to 2,700-3,200 RPM and you will most likely notice the horrible vibration is gone. Replace the bolt with a clevis pin, a couple of fender washers, and a couple of rubber washers. (You often see this referred to as the "Clevis Pin Mod"
This will keep it from falling off the bike if the rear bolt comes lose but it will let it float a little and remove the solid attachment that causes the resonance and vibration.
Should Harley have addressed this issue? Yes, I think so. But spending the 5 minutes and $5 at the hardware store to turn the FLD into a great riding bike beats arguing with them forever.
Tim