I truthfully, seriously, dont see what the big deal is when it comes to the BC key requirements. I see a log of "Its long" or "It takes effort"
And that's it. It's. Too. Hard.
The entry-level full-size instance is SSC. To even get in requires a very long attunement chain within Karazhan - out of reach for most casual guilds. It also requires killing Gruul - impossible for casual guilds.
The point about level 70 ~= attunements is a good one. YOU DIDN'T HAVE TO BE LEVEL 60 TO ZONE INTO MC. So yes, you're quite right. You shouldn't have to be level 70 to zone into SSC.
At the moment, we are at the equivalent point where zoning into the entry level 25-man raid requires extended questing in a 10-man instance, plus defeating an extremely difficult smaller 25-man raid, with no way to gear past either.
A very neat parallel would be if Molten Core attunement required you to have completed your Dungeon set 0.5 (extensive questing in 10-man dungeon as part of this) and to have defeated Onyxia while clad in greens (possible for the very best, or people willing to flask the entire raid). Oh, and by the way, there is no Dire Maul, and Dungeon Set 0.5 is no better than entry level 60 quest blues, so you can't outgear anything.
Still think it's reasonable? If vanilla WoW had had comparable attunements, the vast majority of guilds would never have entered MC.
And the final ***k-you is that there's no ZG or AQ20 either, so you have nothing to do while waiting for the devs to open up the doors and make MC accessible.
But then there's Xi's point. If the first boss in MC was comparable in difficulty to Vaelastrasz (high resist requirements for a proportion of the raid, very tight DPS race), then you won't get any where in there unless you're good enough to beat the insane attunement. So you don't belong there. The average raider doesn't deserve to exist. Gee, thanks. Way to encourage people to try.