A hardcore is someone who is highly motivated to achieve a goal. While this goal may be inside of a video game and therefore deemed "insignificant" to some, it is important to them and is therefore a worthwhile pursuit. Relativism is a wonderful thing. Hardcore does not necessarily connote a specific amount of time played, but is instead about one's mastery of the task. This is because the best "hardcore" raiders will blow through the content relatively quickly (usually taking no longer than a month) and will after that fall into a pretty relaxed schedule of raiding (5-6 hours a week just for gear/alt clears) until tests start on the next tier.