I am way beyond the point where I care about how hard or easy any particular dungeon or raid is in World of Warcraft. But when I read about the Firelands nerf and the reactions to it, I feel as if Blizzard managed to make everybody unhappy. I do believe that a good MMORPG could be made with raid content that is accessible to the majority of players, let's say down to average player minus 1 sigma, which would be 85% of all players. I also believe that a good MMORPG could be made in which only the players at least 1 sigma above average have access to raid content. But the important thing is to chose one model, and then stick to it.
Right now, if somebody asks you the question whether raiding is hard in World of Warcraft, you need to reach for a calendar to give an answer. Raiding was hard from this point in time to that point, then it got harder, then it got totally easy, then it got hard again, and now it's being nerfed to easier again. And every time the difficulty changes, players have to adapt.
In a multiplayer game, the question with who I can play is of extreme importance. If the game has a difficulty level which basically allows nearly everybody to beat the content, or at least gives a group of more competent players the option to "carry" their less competent friends (e.g. 40-man raids), people choose who to play with on the basis of social criteria. They play with their friends, with people they like, with people who are agreeable to hang out with and have fun. If the game has a high difficulty level or other reason for a team to play "at least this well" (e.g. for a competition), the criteria for team composition dramatically change. If you plan a fun bowling evening with your friends, your selection criteria are different than if you try to assemble a bowling team for a local championship. Both methods of team assembly are valid, but as they are done in response to the challenge level, you can't have the challenge level fluctuate wildly without that having serious consequences.
Thus I would really prefer Blizzard to finally chose a side, and tell us what they want their game to be. Ideally they'd make the leveling game consistent with the end game. The situation that drove me away from early Cataclysm was one where the leveling game was too easy for me, and the endgame too hard. Blizzard either should be consistent with their Raid Finder plans and from now on only make raids which a pickup raid group of average players is actually able to beat, or they should make a leveling game which offers some challenge and culminates in a hard raiding endgame which then isn't nerfed just weeks after release. Decide, Blizzard, and stick to your guns. Listen to President Lincoln: “You can please some of the people all of the time, you can please all of the people some of the time, but you can’t please all of the people all of the time”. World of Warcraft is suffering from trying to please all of the people all of the time, and ends up see-sawing between different models.