First of up:

Windows 10 x64
AMD Radion HD 7770
Latest drivers (released July 29th that upgrades support for Windows 10)

This actually started when I upgraded to windows 10 but before I upgraded to the latest drivers. It continues after I upgraded the drivers.

I've noticed when I'm jumping locations a lot (whether to a dungeon or zone changes due to hunts) my framerate drops considerably. It's not consistent on when it happens but just randomly happens. I'm talking going from 50-70 fps down to 15 fps. It will hold there from then on out. The only thing I have seen that temporarily fixes the issue is switching to another display default (such as desktop (Normal) or Laptop (High)). However given another few jumps, and the fps will drop again.