Heart of thorns badly optimised?
https://forum-en.gw2archive.eu/forum/support/support/64-bit-Client-Beta-FAQ/first
I believe you will find your answer here,
You are running a Geforce 840M, which im guessing is a laptop if im not mistaken, you may have to tell the x64 client to use your 840m, as chances are its using the intel on board one, there are fixes for this issue in the above link.