Hardcore players are frustrated with game changes that benefit more casual players. Casuals are overwhelmed by the amount of play time required to be competitive in the endgame. This brings up the question of who deserves to see the complete story unfold.
Seraphina of Baelgun brought up the issue of accessibility to endgame content on the WoW official forums. Like all of the other Warcraft games, WoW has an interesting and compelling story line, with several sub-stories along the way. While all players pay for the same content, not all of them can experience it. In many role playing games, once you've played through certain story line elements you can access the endgame content. Relatively few players will be able to complete the Sunwell Plateau prior to the release of Wrath of the Lich King, just as relatively few players were able to down Naxxramas before Burning Crusade was launched.