Hans,
What do you mean
"I of course disagree with Dave Jackson, ..." 
The following are a few specific responses to you concerns.
Efficiency: All rotorcraft aerodynamists will say that current helicopters are extremely inefficient, in both hover and forward flight. A couple of reasons are;
- The tail rotor consumes between 8 to 15% of the power, depending on whether a Western or Eastern (Kamov) spin is put on the information.
- In fast forward flight, the root of the retreating blade and the tip of the advancing blade are imparting a downward (negative) thrust on the craft.
Elimination of the tail rotor is very, very easy. Developing Active Blade Twist will be very, very difficult. But, both WILL be done.
Yaw Control: Yaw control can be achieved by;
- Opposed cyclic, on twin rotor craft
- Differential collective, on twin rotor craft
- Lateral differential cyclic, on the propeller(s) of horizontal thrusters
- Rudder or deflectors, if located in the airflow.
Early Advanced Helicopters The two helicopters are the
Flettner FL282 and the
Focke Achgelis Fa223 . Both were in production during WWII. At the end of the war, Germany was restricted from continue with the development of their aircraft.
Many, many moons ago Mr. Glidden Doman chaired a dinner meeting of the American Helicopter Society. Both Anton Flettner and Igor Sikorsky were present. After the dinner, an 8mm film of the Flettner FL282 was presented, which showed the
technical details of this craft. Mr. Doman told me directly that Igor was very obviously taken aback at the technological sophistication of FL282.
Flettner FL282 Transmission & Rotors shows a rediscovered and refurbished transmission & rotorhubs. For a 60 year old helicopter, it is quite something.
You mentioned
"Remember the german machines had serious metal fatigue problems that limited the life of many components to something on the order of 20 hours.". The only reference to 20 hours that I can recall is from Prewitt's evaluation of the Fl282 after the war. The Maintenance section of the report says
"It was interesting to note that during the twenty hours of flying this machine, no difficulties occurred in regard to maintaining the helicopter in flying condition."
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Nick,
Your points are all valid, but I think that advancements require both the dream of concept and the reality of detail.
At the risk of overselling one specific craft, Flettner and Hohenemser made a beautiful team. Flettner was the dreamer who kept on coming up with wild and wonderful ideas, whereas Hohenemser was the engineer who kept bringing Flettner back down to earth.
There must be a new future for rotorcraft, and I suspect that it will arise, in part, from the likes of Stepniewski's " Low Tip Speed Design Philosophy" and Sikorsky's "Reverse Velocity Rotorcraft Concept"