Honestly, the "lead the by the nose" situation is a large improvement from many of the doctors I've met, who will actively ignore any evidence that doesn't fit their favourite diagnosis. Classic example: my partner was impaled through the leg in a workplace accident and had to go to the ER. The doctor declared that the wound was, in fact, a diabetic sore and that my partner had faked the accident to cover it up. Since the "diabetes" had reached the point of developing sores, he was prescribing insulin. However, the insurance company, "as a formality", insisted that he measure her blood sugar. After TWENTY blood tests came back with a perfectly healthy blood sugar level, he stuck with the diabetes diagnosis and just prescribed a different drug for it.

A runner up was a co-worker who WAS diabetic after a pancreatic infection. He later went to the doctor to complain about some knee pain. The doctor looked at the symptoms (e.g. joint paint, diabetes, shortness of breath) and diagnosed asymptomatic obesity. The "asymptomatic" part comes from the fact that my co-worker was built like David Bowie. However, the doctor declared that the remaining symptoms pointed towards obesity and that losing forty pounds would clear up all his issues.

For reals. I have alpha and beta thalassemia minor. It causes funny bloodwork (namely, it looks like I'm anemic). When I first got my results, doctors wanted me to see an oncologist and cardiologist and do all these tests and procedures. I thought it was odd because my bloodwork had always come back this way, so I researched a bunch of conditions that could cause the numbers I had (because my numbers weren't quite conducive to cancer or heart problems either). Anyway, I realized after making lots of lists and ruling things out that I likely had mild thallassemia, and when I finally got tested, it turned out I did.

No surprise there given my ethnic background (which frankly should have been a dead giveaway, because thalassemias are not uncommon at all), but I saved myself from being put on iron supplementation which is already potentially dangerous for a man, but especially dangerous to someone with thalassemia.

The closest we currently get to scientific method in medicine is via double-blind large randomized trials, which is not applicable for a single doctor's practice.