I agree with your general sentiment. I think the distinction should not be between WoW and real life, but between real skills and fake skills, between real progression and fake progression, and who is controlling the experience.

In WoW, your character has several skills, stats, and abilities that define it. You choose which ones to work on, how to shape your character, and then you put in the time to make that happen. But what about your skills? You are not getting stronger or better at wielding a two-handed weapon. You are getting better at playing WoW, you are improving your hand-eye coordination, you are bettering your combat-driven teamwork abilities, and you are getting better at determination: being patient and working towards a goal.

The problem comes in the illusion of progression. Your character improves almost continuously, building its skills to a point where it is better than all the other characters. Eventually your character reaches a ceiling, but you can always create another character with different skills and do it all again. But you stop progressing much sooner. Early on, your ability to play WoW tapers off to a suitably-high level such that the real gain is in improving your character. You master the conventions of in-game communication. You develop a routine and diligently set to work improving your characters without question. You stop progressing.

But what happens when you reach that ceiling, when you become the best? In WoW and many other video games, the game ceases to be fun when you are as powerful as possible. Since someone else owns the experience, you are stuck waiting for them to tell you what to do with your newfound abilities. This is why I regret the time I sank into becoming an Expert guitar player on Rock Band. When your playing abilities max out, the game becomes a chore, even if you don't realize it. The best rhythm game players spend their time playing the same songs over and over again in an effort to play them flawlessly. The game ceases to be a game.

In "real life," if you manage to "max out" a "real skill," you can actually do something else, anything you want, with it. Rather than hope that song that I love comes out on Rock Band so that I can put my hundreds of hours to work playing it, I could have spent hundreds of hours playing real guitar and be able to play any song. If I sink a lot of time into becoming a great comedian, I can hit the road, make people all of the place laugh, and make money doing it. If I spend time improving my health and fitness, I can run marathons, play competitive sports, or become a vigilante hero. The choice is entirely up to me.

That's what it boils down to. Is your leveling work tying you to a system where you can't control the direction you're heading in? In play, in art, in work, and in life, make sure that the skills you're improving are flexible in a way that allows you to apply them in any way you wish. Otherwise, you're just playing someone else's game.

Note: I used quotes around "real life" and "real skill" because I'm cheating by defining them somewhat circularly. A "real skill" is a skill that can be applied in many different ways, limited only by creativity. "Real life" is the arena in which you practice and execute those real skills.