Gamepad on PC...

[Esp]

This is so odd, I use a controller on PC as well, and have been since ARR beta and I haven't experienced the issue your describing, even after updating for Shadowbringers (Using PC launcher, and not through Steam). Even went through the patch notes and the current issues sections in them to make sure nothing changed for controllers, and for sure there has not been.

You say your using the same controller you have always used, and it isn't Steam that's the issue. Have you tried playing other games that allow you the same freedom with the camera and tried to replicate the issue? Maybe it isn't Steam or FFXIV, but your controller that's wonky.

Years (or months, depending on how cheap a controller you get) of wear, tear, drops and constant use can start causing issues. If your controller also has a App or program that operates it, then maybe you can check the settings and adjust things so it's back to normal.

Just some thoughts.