This isn't anything new, though. Almost any guild could clear most of heroic ICC once the buff was up to 30%. The same thing applied to practically every Burning Crusade raid with the WotLK patch (30% nerf to everything, save Hyjal).
This has happened before and it'll continue happening at the end of every expansion. You said that MoP raiding is a "big turn from cata raiding..." and that makes me wonder if you raided BWD, BoT, and To4W at the start of Cata. I'm guessing you didn't, because some of those fights were just as difficult, especially once you got to heroic modes. Certainly more difficult than heroic DS.
Either way, as I said, this is going to happen with every final raid in every expansion. The only people not used to it are hardcore raiders (since they don't have problems killing stuff anyway) and those who just started the game or just started raiding.