Well, figure there's 168 hours a week, you sleep 8 a day so that's 54 per week, so you're awake say 114 hours. If you work 40 hours, plus maybe an hour a day commute, that's 45 hours. So now you're down to 79 hours. You need to eat and such, figure that's 2 hours a day between eating and preparing food, so 14 hours there. You have 65 hours left still. You need food so you have to go shopping and run other errands, maybe 5 hours a week. You go out with friends to bars or whatever twice a week, that's another 6 hours or so. Now you're down to 54 hours.
That's 54 hours to do hobbies or other not necessary things. Assuming you enjoy multiple hobbies, maybe you golf twice a week, that's about 10 hours. You like a few shows on TV so you never miss them, that's another maybe 5-6 hours, hell you watch your favorite sports team 5 times a week, that's 15 hours. That still leaves you with 24 hours a week to play WoW if you want. That's *significantly* more time than you need to succeed in WoW. You can raid 3 nights a week for 4 hours a night, farm all the mats you need for like 3 hours a week, and then PvP/heroics/LFR whatever for 9 more hours.
So, basically, that's about how it goes.