This has been my experience also. After a while away from the game, I upgraded from the 32 bit client to the 64 bit client because the 32-bit client would not work once I upgraded to 10.12. The 64 bit client now works, but performance is terrible. PvP, WvW, and large events used to run fine to tolerably at moderate graphics settings; I can now get them to work if I turn the graphics settings to bare minimum. Bare minimum gives me about 35 fps, "autodetect" gives ~10 fps. 35 fps was low-end on autodetect previously. iMac 2011, 10 Gb RAM, 4 Tb external firewire drive.