I have the exact same issue. My computer is a custom build, top of the line machine. It can play all modern games, such as dragon age inquisition, on maximum settings with ease. Regardless of settings, I sit at or below 30 fps in every zone. GW2 has always been poorly optimized, but this looks to be a problem with new hardware and old software. My computer specifications can be found below.
CPU – i7 4790k
GPU – GTX 980
RAM – 16gb DDR3 1866