While you might have the x64 installed, that does not mean that you are actually running it. Go into Task Manager, click processes, and check if wow.exe or wow-64.exe is running when you start your game. If you find that wow.exe is running in your task manager, I've got good and bad news for you.
Good) chances are you might be able to increase your fps by quite a bit.
Bad) Your technological incompetance has lead you to believe that you automatically ran the x64 by simply having it installed, something that of course is not true, and you have never actually experienced wow-64, yet you roam about on internet forums telling people about your x64 experienecs, while in reailty you dont have any, making you kind of the bad guy here.