Now before I explain why I think the distinction between hardcore and casual is useful, I think it's necessary that we all be on the same page as far as what hardcore and casual actually are. I found Rossi's argument against the usage of these words particularly flawed because he was working around an assumed and rigid definition of what a hardcore player and a casual player are. Toward the end of his article he pointed out that the casual/hardcore metric doesn't work when you consider the various ways in which some players are engaging with the game. Not every player raids, he explained, but that doesn't mean they can't be hardcore.
Now, I agree with that for the most part, but I disagree with his understanding of hardcore and casual. You see, hardcore and casual are not and have never been part of any metric. It's actually impossible for them to have ever been since the definition of casual and hardcore is subjective. Ask any two people what kind of behavior distinguishes a casual player from a hardcore player and the answer will be different in some way ... And if the definition of something varies from person to person, it can't logically be used as a standard of measurement.