Quote from Blizzard staff
Raids & Dungeons - Hard Mode
Ulduar has a ton of bosses. While I'm sure some players would love for us to deliver an instance with that level of content every month or so (and throw in a 5-player run to boot!), it's not in the cards, at least not for the next couple of years.
Instead, what we tried to do with Ulduar is offer a lot of different ways to play the encounters. While the progress-oriented guilds may clear it quickly, we hope that some of the hard modes will offer them a lot to chew on. All of the players who are somewhere between barely being able to clear the instance and the "world first" crowd should be able to find a comfortable difficulty level as well.
Your old model towards end game was a success, it brought you eleven million players.
Most of whom never had a chance to finish a raid. They didn't get to see some of the best art in the game, hear the unique music or voice over, or in many cases even see the villian at the end of their quest line. From a production POV, instances are very expensive. It seems an odd choice to lavish all that attention on such a tiny percent of the player base.
At the same time, we know there are players who love a challenge and are willing to do almost anything to beat a raid-destroying boss provided they also have a shot at the best loot. They don't want the instances to be over too soon. They like banging their head against the wall.
And so hard modes were born. We tested the water a little with Obsidian Sanctum. We're going full bore with Ulduar.