Looking at this...
I think the first boss is a bit superfluous. I think that they could have picked something else besides an elemental. Its place in the raid feels a lot like Morchok.
It looks like half the instance (up to sha) takes place in Pandaria because of Norushen. If I'm not mistaken, he was inside the vault of Yrshaj in that scenario. I'm not sure how he would get to Ogrimmar.
The way it's designed, it feels a little like two raids instead of one. I'm excited for the second half.