Make sure your OS audio settings match your physical set-up, as well as the in-game settings.
You definitely set up your speakers to have a center speaker (5.1/7.1?), but you only have stereo (2.0) or quad (4.0). You should check your speaker configuration in Windows and the game.
I’m having tons of issues with voiceovers on all my characters. It seems that I can not be directly facing an NPC who is speaking, or i can’t hear it. I also can’t hear my own voice in a lot of places. The NPCs have to be on either the left or right side of my character. ANy ideas or is this a known issue?
I believe that GW2 does not support Surround 5.1/7.1 Sound. Therefore, you can not hear certain channels.
Change to stereo (i.e., dual) channel in your Windows sound settings, and that should solve the problem.