In one way I agree that everyone deserves to experience certain content in it's entirety, therefor having lower difficulty entry raid(s) would make sense, at least in a population stand-point. On the other hand; the Outland server is always there for that, and if Medivh had not been announced as having hardcore and challenging raids, that would definitely make more sense.
Then again, I think having really hard entry raids to begin with is a good thing, as they can always nerf them, just like Blizzard has done. Everyone is happy in the end, first the hardcore gamers who get to 70, for the most part the quickest, who are looking for the challenge and feeling of reward when downing a difficult boss, then later on the more casual players who get to 70 a bit slower, and just want to experience the raid without having to be complete masters of their gameplay and whatnot. This would only make it fair for everyone, especially on a server that has been advertised as a certain type of realm.
Basically, I think even entry raids should simply not be easily cleared, even on release, I would agree with a nerf after a set period of time of after a certain release of next content.
Thinking back, some kind of feature that would actually start off as super high difficulty values to bosses that would decrease over time up to a certain point would be kind of cool, but that's just my opinion