I really don't think LFR's that hard, even on my 517 Pally. Answer UNACCEPTABLE! :P
I do think that it's a combination of factors. The tanks playing catchup on gear, such as yourself Agg, are only going to do specific wings to fill out item upgrades for weapons/shields, the rest of the gear you're better off farming Burdens of Eternity or Heroic Throne of Thunder, or running Flex, maybe with guild or openraid if not.
Most of the Normal mode tanks who aren't playing catch up, probably do have fully upgraded Tot Normal gear, 530 ilevel. LFR only drops 528, which if you have the valor spare to upgrade is fine, if you don't because you're clearing a few normal modes or getting burdens or getting Flex gear, and lets face it if you where clearing normal ToT you'r probably quite capable of clearing SoO Flex, so you won't have the valour to spare (because you're much more likely to spend it on drops from elsewhere), a 528 piece isn't an upgrade. over your 530 ToT gear.
I do think that's a big reason, obtaining gear is probably the biggest motivation for going into LFR as a normal mode raider. People can claim that obtaining gear isn't important to them, and that's fine they may say they raid for the challenge or to have fun with friends and I can sometime believe that, but those aren't factors in LFR. you're not doing it to hang out with friends, and the only challenge LFR provides is overcoming other people's stupidity, and quite frankly I am not up to that challenge. I can see a lot of the guys who just want to hang out with their friends and raid will do flex instead of LFR, its them hanging with their buds , they aren't going to have to deal with some random gits, just their own gits.
SO with those types of tanks out whose left? the tanks that couldn't do normal last tier and haven't geared up from Flex yet, the alts, the casuals, the guys who don't have a lot of time for wow and the guys who don't have any in game friends; the guys where LFR is their Endgame. For them i can accept that maybe LFR is a challenge for them, but I really don't think sort of guys really role tanks that often, being an unreliable tank casual tank just doesn't get you invited anywhere, in my own experience, if we have a healer or DPS have to drop a night its generally fine, if we have a tank drop the RL is more likely to call the night than pug. And these guys are the tanks that get called out in LFR for screwing up, especially when partnered with an equally inexperienced co tanks, helaer and DPS, and i can't really see why they'd stick at it, why tank when you endgame consists of people yelling at you, why pay 8 quid a month to log on for a 45-120 minutes of abuse 4 times a week, screw that I'll just go DPS instead.
aslo Taunt swaps. NOT HARD. and really overused now. last 2 tiers have really lent on them as a mechanic, imade a list of the bosse sover the last 6 tiers (post-wotlk) over half of them have taunt swaps. its so fucking boring.