I didn't read your whole post, I skimmed it and deduced what you were saying from other people commenting before mine. Just to let you know...
As a former "regular raider" from vanilla to early cata and since then having never stepped foot in a raid I say these thoughts....
Generally speaking options are good, lack of options are bad.
Different difficulties are good -- because its different options. BUT these different options only work if the reward is sufficiently matching the challenge, if that doesn't exist then I can easily be swayed in saying that is wrong and then the different difficulties need to be worked on just the "risk / reward" value alone. However if the hardest difficult rewards significantly better gear than the easiest difficulty my comment at that point is "what's the problem then?".
Assumptions don't equal reality. One of the main assumptions for arguments against multiple raid difficulties is that it dilutes the available player pool for the more challenging difficulties (because the theory is people are choosing the easier way to get geared, despite it being lower level gear). I personally think that is a stupid thought. If you want to sincerely do the hardest content you WILL find a way to do the hardest content and you won't settle at say "LFR"... the people that settle for the easier stuff are most likely there because that's fine for them and they aren't dedicated raiders...these people you don't want apply to your ultra hard core raid group anyway!!
The whole time assumption thing - example "...and don't tell me you don't have time to raid...*I* was able to do [x, y, z] in [a,b,c] amount of time".... of all things this makes me laugh the most....why don't people understand such a simple concept -- how YOU spend your time has NOTHING to do with how I spend my time. Why? Variables like -- my level of interest in the game is probably different than yours. If you are excited to raid on any given night but my attitude is simply "yeah I guess that would be cool"...then sure you probably will and do get more accomplished in 2 hours of raid time than I do because you are more motivated about it. Also you don't know my list of real life responsibilities anymore than I do know yours...not to mention maybe I don't want to spend as much as my free time playing a computer game as you do....I mean there's endless variables which is why one of the biggest things I hate in these debates is when people judge someone's time....that's a bullshit reply to say "Well it only takes 2 hours to x many times a week" or whatever your argument is...
Epeen. Finally I can't help but think topics like this have at least something to do with epeen....raiders of today simply don't like that other players , having an easier time, get to see the same pixels as they do - thus in ego ridden minds that dilutes their 'epeen standing' in the virtual community of the game.
And if the epeen issue is the reason - that's a personal issue....not a game one. Learn to be humble, learn perspective in life.