I play WoW but i've never gotten too addicted, like, when one of my friends or my family tells/asks me to come/go over to someones house, i will because i have alot of fun doing some stuff like that, i also have a friend who was obsessed with WoW but he played it for like 2 months and then got bored(but theexpansion will be comming out sometime so i bet he'll become a hardcore gamer once again)

I think you just gotta try getting him to do something he really likes that doesnt involve what you're trying to get him away from

or you could possibly try and get into the parental controls for WoW and limit him