Addressing one of your questions...
The idea is that a pdoc is there to provide an accurate diagnosis.
Do all pdocs always provide accurate diagnoses? Probably not
But there is probably a better chance of a pdoc giving an accurate ''diagnosis'' than me for example since I do not have a degree in medicine/psychology.
I think that even a ''mediocre'' pdoc may be of more help to you than an ''average'' GP. GP's really are NOT trained in psych. And in my experience, some of them are worse than useless.