oilman,
In term of diagnoses of the causes of damp I think the fundemental problem is that it is too few surveyors are capable of, and too few clients are prepared to pay for, proper investigation.
Sometimes it very simple to diagnose the cause, the cause being readily apparent. However, much of the time those obvious solutions fail (even if they improve things a bit). I am certain that you will find people posting here who have had a persistent or re-occuring problem that they have never been able to cure. However, it is entirely posible to diagnose and cure almost all damp problems given the right equipment, knowledge, time and strategy.
The BRE published a method for diagnosing the causes of damp which is perfectly sound (BRE Good Repair Guide 33). It has also published more specific guidance on the diagnoses and cure of particular problems including penetrating damp, rising damp, condensation and leaks from service pipes. All these things have particular tests that can be carried out with appropriate equipment and can give pretty conclusive answers.
It is certainly true that one cannot positively diagnose rising damp (or any other cause) with an electrical resistivity meter (protimeter) alone. However, you can get a definitive answer with a speedy moisture meter (which costs about £800 and involves taking core samples from the walls). I cannot say there is no such thing as rising damp (scientifically the jury is still out on that one), but I can say that I have never seen it. I have seen many other things diagnosed as rising damp.
It is true that improved insulation has caused many problems with condensation in older buildings which were not designed to be insulated, but the fact is that we live in the 21st century and people don't want to live in draughty homes. We also have environmental problems and need to save energy. So even if draft proofing is a problem the answer is not to condemn draught proofing but to design energy saving measures in a way that doesn't cause these problems. I do it all the time.