The biggest difference is that this buff is being added slowly. It would feel a lot more jarring if on Monday it was "dear god this is hard and only 5% of guilds have gotten through it" and on Tuesday there was a 30% buff all of the sudden and the number of lich king kills had tripled by Friday.

I think Blizzard has the right idea with a slowly increasing buff. The earlier you killed the lich king, the cooler it is because (1) you got there first and (2) you got there with a lesser handicap. But at the same time, a lot of people will eventually get there. Essentially, if you are part of a raiding guild, Blizz would like you to eventually reach the lich king.

And frankly, I think that's a good idea. Blizzard put a lot of time and effort into designing this content and would like more people to see it. A lot of players would like to see it, and otherwise wouldn't be able to.

Does it cheapen the experience of hardcore guilds? Maybe a little. You still get there first, but you don't get to stand there alone for very long. At the same time, WoW was never really a "hardcore" MMO. The true test for elite guilds in WotLK was Algalon, and I think that's appropriate. The world and the storyline was centered around Arthas, so everyone who wants to should get to see him. Algalon was an awesome, epic encounter (all the more so for the "attunement" of keeper hardmodes), but it is for the best that he was not an important character in the lore.