It may not have been that the drug was incapable of meeting your pain needs. I was on the fentanyl transdermal patch as well, and was having absorption issues resulting in the patch wearing out unpredictably. When I moved back to oxycodone from fentanyl, I went through basically the same thing you describe when you switched to Zohydro. In addition, I also went through intense opiate withdrawal despite being on opiate therapy (again, pretty much as you describe, though shorter in length). There are certain people who fentanyl affects that way. It's phenomenal when it works right, and hell when it doesn't.
I'm glad I wasn't on fentanyl for long enough to go through the lengthy withdrawal you did; I got off it in relatively short order and will not ever again use the transdermal form.