There are a lot of reasons why the LFR queue is so long these days for the average player -- ilevel requirements (though Blizzard's made it easier to get gear from older raids to address this), the sheer popularity of new content, and, as Ghostcrawler pointed out, tanks and healers who queue with their guildies -- but I think Grumpy Elf has a point.
No matter what, you name it, everything in the LFR when done wrong screams "the healers will fix it". Dropping the bad where it should not be, no worries, the healers will fix it. Not using your defensive cooldowns, no worries, the healers will fix it ... even in the LFR if you do not follow mechanics it hurts and puts all the pressure on the healers.
While I've mostly tanked in Mists of Pandaria, I healed my way through the Raid Finder in Dragon Soul, and the number of players who took unnecessary or avoidable damage was depressingly high. You expect that with anyone who might be new to the instance, but it wasn't fun seeing a raid with lots of people in normal or even heroic tier 13 ignoring, say, the players trapped in Hagara's Ice Tombs.
So for the healers out there, here's a question: Are you queuing for Raid Finder raids? If you are, is the job noticeably more difficult or stressful than it is with your guildies? If you aren't queuing, why not?