Given I've seen people struggle to get their meta gem with equal ilevel to me (as an LFR-raider myself), while I walked in and one-shot the Thunder Forge fight, let the solo parts be the benchmark and skill-check to see if it is worth it for you.
Flex/Normal/Heroic raiders will have a leg up on LFR raiders, due to gear levels allowing them to get through mechanics faster. Those of us who have kept up with the progression of the chain, with the implicit statements that the Legendaries will be available to everyone... guess what? If you got the skill to do the solo parts, on top of the time to sink into the raid-progression/grindy parts, then you are rewarded. Hell, the people who earn it in LFR gear should be entitled to more: They did it with a gear handicap over those with a higher ilevel from "real raiding".
I managed the Thunder Forge quest at about ilevel 505 at the time (and yes, I am a Ret Paladin). I've seen people with 515+ fail, horribly, at it. Individual skill sets the bar. Gear helps, but frankly, who's doing the harder version of the solo content, the LFR raider, or the Heroic one? Yeah, guess what, that would be the guy in the 530+ gear, not the one in 502 gear. The content scales down as your ilevel goes up, so those of you running Normal/Heroic for 5.2's content have an ADVANTAGE over the LFR raiders. If we are succeeding, it is by merits of more skill, not "LFR scrub". The fight an ilevel 505 Paladin does is the exact same as an ilevel 535 Paladin, the only difference is the 535 hits harder/faster, and thereby ends the fight quicker, has to focus on survival a little less.
LFR might be the bottom-rung on raiding, but when the LFR raiders with actual skill stand up and do what you did with 20+ ilevels of better gear, it's a problem? REALLY? Elitism much? Not every LFR raider is a fail. Many of us just lack the time to raid with a guild (Hi, I work graveyard shift, starting at 9pm PST, 5 days a week, see a problem?), and use this as a welcome option. How about the guy who was a hardcore raider, still has the skill, but has a family now, so can't dedicate to a real guild, due to a 2 year old son/daughter? Should he be told that, despite dedicating the time he could to progress at a slower rate (reminder: LFR takes over 1.5 months to unlock all raid content that Normal/Heroic get right away or within 1-2 weeks, you do get it sooner, provided RNG doesn't hate you), knowing that his dedication would be paid off, because he can trump over the solo content due to skill and experience with his character, that now he gets nothing, due to changes in life?
Everyone complains that "Blizzard caters to casuals"... many of the people who used to be of the hardcore, dedicated, playerbase of 6-8 years ago have grown up, have jobs, families, etc. They unfortunately don't always have the time for dedicated guilds, schedules, etc. But they are the LONG-TERM customers who have been paying every month for the last 6+ years... not those who "Oh, this tier is done, cancel sub til next patch", who are only still active right now cause RNG has hated on them for quest drops for said legendary chain.
Legendary items were first and foremost pure, dumb, luck.
Classic: Bindings of the Windseeker and Eye of Sulfuras, were both like 0.1% Drop chances or something. Similar for the quest starter for Aitesh (though that one I am a lot foggier on, never saw one finished during my time in Classic, as we never finished Naxx... 12/14 40-Man)
TBC: RNG, and nothing else for the Warglaives or Thorai'dal.
WotLK: I was raiding 10M during WotLK, so I didn't see them at all. Val'anyr was RNG on getting fragments to drop per boss, then you threw them at the last boss, and BAM, resolved, Legendary. Shadowmourne had a LITTLE bit of personal work (not much...) and then similar, but lengthier process to get completed.
Cataclysm: Start seeing more solo-related work involved in the quest lines for both Dragonwrath and Fangs of the Father. Still had elements of RNG though as you progressed, getting the grindy element from bosses of that tier's raid.
Now here we are... everyone can do the annoying grindy part. LFR is slowest, due to the nature of wing unlocks taking like 2 weeks per wing (so 6 weeks for full unlock), where as Normal is open fully at the start, Heroic the following week. Flex will likely to being on 1 week unlocks per wing, based on the description of it from the CMs so far. Maybe Heroic should have slightly better drop rates than the other formats for the quest items, but that is the grind. It doesn't take skill to finish, just RNG.
Skill comes in from the solo components. I've heard of Hunters bitching a ton about the Wrathion cloak fight, with like ilevel 530 gear. If that's the case, I look forward to the fight, cause when I finish it at ilevel 515 or so, it will be hilarious.
tldr; If you raid above LFR, you are actually nerfing the content of the legendary quest, by using higher gear for the solo fights. Don't talk about exclusivity when you get an advantage in the first place.