First of all, to start off with something positive, I think there are benefits to playing wow and games in general. Besides the scientifically proven benefits of improving your reaction time, focus, multi-tasking skills, etc, it can also help you clear your mind. We've all had moments when we just didn't want to think about our real life or were too excited about something, so we wanted time to pass faster, and WoW is a great way to do that. So, no, not *everything* is better than WoW.
Moreover, there is again nothing wrong with spending your free time online if that is what makes you happy. The point is that you're still creating experiences and socializing, and online socialization is still better than none at all. I've made many great friends in this game, and there are moments that I still happily remember from years ago when I first started. In short, my general "rule" is that if it makes you happy, it's worth doing.
Now, how much is too much?
I think it depends on your lifestyle and obligations. When I started playing this game, I was a depressed teen with no real friends spending 10+ hours online, like you said. I was smart, so studying for an hour or two every other day was enough for me, and the game didn't affect my grades. But without this game, I feel like I would have just fallen deeper into my depression, as I'd still have no friends and be stuck home with a family that doesn't understand me, I'd just have no way to vent and disconnect.
- unlike Invictum ^, I was depressed despite the game, not because of the game -
Just like you, I eventually moved on, as I switched to MOP after molten, and MOP died out. And yes, I agree - finally accepting that you don't need to log in is the hardest step, being comfortable with not being online. After you make that step, it's much easier to control what was once an addiction.
Now, I am a 25+-year-old with a job, friends, pets, and working on my Ph.D. studies. I always have more important things to do, so for me, anything that affects my actual responsibilities is too much. I need to respect my work deadlines, I need to finish college stuff on time, I need to get enough rest to function, I need to eat, and all those things come before WoW. And I am fine not logging on for days, I know nobody will actually "miss me", my guilds will be fine, I won't get kicked because my GMs understand that real life comes first, etc. I am comfortable not playing every day if I know there are more important things to do.
In short, it depends on your lifestyle. Real life always comes first.