I thought I would put in my two cents to answer a question no one asked me. The whole argument of looking for raid being required content or not.
I will give you the perspective of a casual raid leader. One that has never been in a world first guild or even a server first guild. Server 8th is the highest we ever got and that is only because it is a smaller server. So we are not a great guild but I believe we are a fair representative of what it means to be a casual raiding guild.
Now, with the back story it is time to give my opinion.
Looking for raid is required content. Anyone that says anything else fits into one of three categories.
1) An exceptional player, the type that finished MV week one while only in heroic gear and some crafted gear.
2) Someone that likes to think they are an exceptional player but rationalizes the fact they still have not downed any bosses in MV as their guilds fault, their lucks fault or anyone elses fault but their own.
3) Someone who doesn't want to raid or would rather wait to be carried.
Now, why do I believe looking for raid is required content?
If I am assembling a guild run I will ask people if they have done the LFR. The reason for this is that it makes it easier to explain. People might have done it 100% wrong in LFR but at least when I explain things they will know the room layout. Another reason is that if people are not willing to gear themselves up do not expect me to carry your ass. Raiding is a team event, one that everyone should contribute to. Doing the LFR is you learning the plays from the playbook. Any decent team player at least checks the plays out before showing up for the game. If you can not be bothered to run LFR to try and get the 476 chest I can not be bothered to drag you along and let you roll on a 489 chest that someone else actually worked for.
For ANY guild that did not clear MV before LFR came out the LFR is required. If it were not required for you and your guild you would have cleared MV already. Simple as that.
Now, look at the math, the number of guilds that completed MV before the LFR came out and the number that didn't. The number of guilds, less that 1% I am sure, that cleared it before the LFR came out did not need it so it is not required for them. For everyone else, the 99% of the player base, LFR is required content.
One note I would like to make about this however. It is only required now, at the start of the expansion. Later on, we will move into the next tier with full gear from the tier before, so LFR becomes optional, it is not needed. You can run it to get some pieces you never got from the previous tier but the previous tiers gear will easily be enough to move into the next tier with. Being this is the beginning of the expansion is why it is required. When people are starting the gearing up process.
Later on, LFR will be for quicker valor capping, alts, and trying to get pieces of a lesser quality that you have had no luck with in the real raid. It might feel required, but it is not. Now, it is required. Later, it won't be. But I will still ask people if they have done it and with two equally geared and equally skilled players I will always choose the person that did the LFR over the one that didn't. So perhaps, even later, it will still be required, by the 99% that is.
Yeap, LFR is required content for any player / guild that can not clear the content easy without it. Basically that means 99% of the raiders out there.
For my raiders, LFR is required. That is just how it is, it makes it easier for everyone.
Just because you can do a raid without 476 gear does not change the fact that 476 gear will make it easier. You can do a raid without gems, you can do a raid without enchants, you can do a raid without reforging, you can do a raid without flasks, you can do a raid without potions, you can do a raid without food, but do you? Nope. Because having those things makes you better, makes the raid easier. If there is something to be gained in the LFR gear wise, it is required to try and get it, just the same as all raiders should be required to gem and enchant.
It might not seem standard now, but once upon a time gems, chants, food, flasks, etc where also considered extras only the hard core players worried about and now they are the standard, they are required. Just like LFR is, or soon will be.