The tradition of making big plot stuff happen in big groups is not unique to World of Warcraft, but it was one of the first games that put all big plot stuff there. Most story content in Final Fantasy XI required just a full party to experience, Final Fantasy XIV requires a mix of light parties and full parties and all of it can be queued, and Star Wars: The Old Republic puts most of its big story confrontations into personal instances. And some players complain because the result is that these face-offs feel less epic.
On the one hand, I disagree; I certainly feel that fighting Xavius in the Emerald Nightmare is less personal rather than more so because of how many people are there. On the other hand, it certainly does mean that the fight can have a much bigger “budget,” so to speak, and the boss has room to really be a full setpiece battle for everyone. What do you think? Does bigger content in an MMO feel more epic to you?