The same sort of lugging vibration will occur in any gear if the rpm is low, however, in the lower gears it tends to be a brief irritation since it doesn't take long for the car to accelerate above the lugging region, then of course the cycle is repeated immediately after the next upshift.What happens if you use tiptronic mode, keep in 4th or 5th at the same RPM as above? (Whatever RPM you see at 32MPH in 6th). Same vibration?
The prolonged irritation is mainly in top gear since the ratio is such that you are now at a speed (30-35 mph) where you may be spending a lot of time.
If there was simply a way to lock out top gear unless you really wanted to use it I imagine most people would find the short-shifting otherwise acceptable. In my car the Sport mode does this, using only gears 1-5, but is not very pleasant driving from stoplight to stoplight since it downshifts to keep rpms above 2k and mpg is lousy. I often wished they did this the old-fashioned way instead, with OD and D shifter positions, instead of D and S. While S can be fun sometimes I really don't have much use for it and would gladly give it up in favor of regular D behavior with 6th locked out.
Anyway, as I said before, Tiptronic is my solution to all of this. I don't expect one from VW.