I get the feeling the redoing the old world took up a much larger chunk of time then they hoped. When you look at all the redesigning they did, it's not too surprising (in my mind at least) that end-game content hasn't been up to people's expectations. I imagine if they were just tacking on an additional continent there would have been more effort into playing the game at 85.
Pure speculation here, but I'm guessing that they felt updating a game that was feeling 7 years old was a better way to increase future revenue then focusing solely on end game progression.
For what it's worth
player activity is still about where it was last summer. I'm guessing the recent bump being indicative of Firelands' release.
I suppose all that means is after all the changes that were made over the last year or so, they're right about where they were.
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That monster in the mirror, he just might be you. -Grover