I am in the camp that believes 5.2 is just a little too soon. A lot of people seem to forget that a majority of 'raiders' had to deal with leveling, gearing up for normal modes, and then actually downing normal bosses. The amount of time that took varied vastly; your heroic raiders (a minority) rushed to level cap in 1-2 days, had workarounds to stuff that normally stalled regular raiders, and quickly dispatched content- because that's what they do.
In no way am I trying to state this as fact, but only going off of information available to me, it seems like most raiders took their time getting to level cap and then gearing up for normal modes. Especially when you're in the mindset still from Cataclysm when your experience has been, 'Why rush? It's just going to sit there for 6+ months anyways' - Yes, blizzard said they would try to push out content faster, but I'm sure most of the playerbase should be excused for being a tad skeptical.
Plus, even while leveling, every other NPC was telling you to 'Slow down! Enjoy life!' I have to say I drank a little of this Kool-aid, and I very much enjoyed the leveling experience MoP had to offer. Jade Forest is one of the most beautiful zones I've played in.
Mini-digression aside, taking into account the leveling process and the gating of each raid, level-cap content really hasn't been out that long compared to what we've been accustomed to; hence the backlash.
It's unfortunate that I probably won't get to clear all of normal modes before 5.2 hits, but I'm not complaining. I know our raid group was a little behind the 8-ball when we started in MSV. Now that people don't have to worry about the whole leveling process, if they keep content coming out at this pace, I believe it would be perfect.