In the end, it is pretty much impossible to appease the hardcore crowd. Between level design, mechanics and art, it takes longer to develop content than it does to complete it. Even if a game launched with 6 months worth of content at a hardcore pace and still have more content being developed, there will hit a breaking point in which the hardcore players will have caught up to what has been released.

The only ways to try control this is through ramped up difficulty or artificial limitations. With ramping up the difficulty to slow down player progression, the company would be spending money developing content for a tiny percentage of the overall consumer base, which no company in their right mind would do. With artificial limitations (such as the fatigue system at the launch of 1.0, mythology tome caps of arr, or the Japanese midnight wait periods that XI had) you end up potentially angering the customers or even hindering the more casual players. In the end, it's really a no-win situation to try to keep the hardcore crowd appeased.