deeper,
'Efficiency' is a comparative characteristic.
I humbly submit that no one would claim the helicopter to be more aerodynamically efficient than its brethren, the airplane. It might also be stated that with a ratio of one helicopter for every half million people, it is obviously not a cost efficient form of transportation. What it does do is fill a niche market. A market that would be bigger, if helicopters were more efficient.
Unlike biotechnology or artificial intelligence, transportation is a mature industry. Yet, I believe that there is room for a significant increase in the efficiency of rotorcraft. Not by 'tweaking' improvements out of existing products, but by developing a new one. This appears to be possible by unifying the old ideas of the Intermeshing Configuration and Advancing Blade Concept with new ideas such as Active Blade Twist and Absolutely Rigid Rotors.
You are definitely correct in saying that
"Some of your theory needs a bit of brushing up also.', but, I would argue that it is better to submit theories for critique then to resign oneself to the status quo.
For example;
The Sikorsky XH-59A ABC was a remarkable craft. It showed the promise of VTOL ~ with fast-forward. Unfortunately, vibration, resulting from an oscillating lateral dissymitry of lift, limited the craft to 230 knots. I theorize
that the craft could have gone much faster if 4-blade rotors had been used, instead of the 3-blade rotors.
The
stuff;
Vibration - Rotor Induced - Analysis of Sikorsky ABC ~ Coaxial
Rotor - Disk - Lateral Dissymmetry of Lift - 3-blade Rotors
Rotor - Disk - Lateral Dissymmetry of Lift - 4-blade Rotors