I'm seeing huge burnouts in everyone I come across to raid with, and that's including myself. And the problem is an easy one to diagnose.
Hard modes are fun, and cool, and I understand how they make it so that one group of people can see some content while another group of people can then do it on a challenging difficulty. LFR further expands on this so that pretty much everyone can see the content now. That's neat... on paper.
In practice, most people are content - even unknowingly so - just seeing the content. They blow through it on LFR or normal mode, they had a blast and beat the game, and then they get into Heroic mode... and the elephant in the room that no one talks about becomes, "Why am I completely relearning this fight and driving my head against the wall because he has one or two extra mechanics, just to get literally identical loot that just has a few extra stat points?" Everyone gives it their best, but after a month or so, people start trickling away. They don't really care about killing hard modes now that even the loot is a cheap carbon copy of gear they already have. The incentive is too small.
It's like spending two weeks beating your favorite single player game, and then immediately turning around and replaying it a second time on a harder difficulty mode. Yeah, I think just about everyone tries it, but only a very small percentage of those people actually continue on and finish the game again - once you know what you're getting into, for most people I've encountered, that's enough excitement to feel okay with putting it back on the shelf.
Which doesn't sound that bad... again, on paper. So everyone had some fun, and the people who really wanted that challenge got it.
In practice, particularly in the World of Warcraft, the content is blown through ridiculously fast and it is assumed that heroic mode is where the actual "pacing" will occur. So I play with all of my friends for a week (and by a week, I mean 3 raid nights total), and then they disappear again, content that they have finished the latest chapter of the book. In fact, now they don't even have to play with me - instead of our MMO group experience, they can now queue up to read that book solo, and get most of the same enjoyment.
We then spend the next few months sadly seeing friends dripping away back to other games, the small percent of players who want to see the challenge through to the end drip away to other guilds, and we worry for another content patch whether the guild will continue to pull through. The next patch will see everyone coming back for a week, although a few have decided to permanently leave World of Warcraft altogether, and the cycle continues... again, and again, and again.
World of Warcraft raiding has become utterly depressing and not fun, at least as an MMO experience.