Yeah, well it's pretty tough to work through all the possible things that could be wrong, especially after going through drug after drug.
They induce a neurological changes that don't necessarily revert immediately after discontinuation.
It's just like weed, you'll burn out eventually. Only the SSRIs, they might lose their effectiveness over years, or so. I don't fully understand every variable in every instance.
The Effexor is the heavy stuff. That's all I know. Effexor, paxil is the lesser evil, then you've got more precision tools coming onto the scene which are supposedly better, and quite possibly better, or really just another round of drugs.
Me personally, I do the shirt run test. I mean I find the stuff I enjoy, and experiment with other things, and the ones that I can tolerate without any immediate negative effects, I'll put them on a slightly higher rotation. Being sure that I do not go too long on any single regime. Tough to do, easy to say, but, yeah, withdrawing from a treatment to see the rebound effects is worth it. Only my opinion.