I still have never seen a single raid/endgame instance above the standard 5-mans. That's a lot of great content I will never get to see as a paying customer for the original and 3 expansions. I don't have the time to sink into being involved in a guild to the point of raiding. If I could somehow show up once a week for 3-4 hours to raid? Sure, I'd love that. But I don't know of a single guild that would let a member do that.
If Blizzard was trying to reach the casual audience more than the hardcore, I would think they'd create modified 5-man versions of the endgame raids with appropriately lowered gear rewards. I'd love to see that. The only thing I've noticed about the game is that they want to help you get your main/alts to high levels faster, so for the hardcore, they can get into their guilds with alts faster, and for the casuals to see a better, quicker sense of progression and less tedious grind. I think their changes have benefited both sets of customers.
I love what they've done to the game, only complaint I have is that I can't access a good portion of content merely because of time constraints. :/