You don't have to spend a lot of time in the game to be hardcore. These types of people usually strive for challenge and try to complete everything while it's still relevant. This requires a bit of a commitment, but by no means does it say you have to play 24/7. While they might more time when new content is first introduced, but after they got the place on farm they really only need to play a couple hours a week.

I used to consider myself as being a hardcore player when I played WoW. My guild only raided 4 hours a day, 3 days a week for a total of 12 hours (when learning), however we put in our best during that time and cleared all hardcore content first or second on the server; content that 99% of the population couldn't do through an entire patch-cycle.