Diagnosis has some value, I'm sure, but is tricky. On the Dissociative Disorder test, I scored 0 for being likely to have it, but that is my main issue in actual therapy. I felt like the test was asking the wrong questions and felt I should have designed the test.
My med psychiatrist asked, off the record, just last week what I thought my diagnosis was (as if I should know) and I replied, "Doc, my diagnosis is whichever illness the insurance company will pay for".