What even is a "hardcore" player? Is it judged by hours spent playing? By the activities undertaken in game? By the ilvl on your main class? It's a pointless label that doesn't really mean anything. Casual at least has a somewhat concrete meaning: someone who only plays a few hours a week. Even then, there are those who will only log in every week to farm the latest coil and be offline the other 6 days. Does that make them casual?