Sound’s Back! I finally figured it out. So basically, I had this app before called “Hear” which boosted audio and it seems that the plugin file which was left behind was causing problems with GW2 Audio.
If anyone does have audio issues, you might’ve installed hear or a similar app before. On you mac, just navigate to /Library/Audio/Plugins and delete the files which came from audio apps you aren’t using anymore.
Hope that helps others having the same errors.
Just read this tip and it solved it for me too! Wished I had noticed this earlier :P