On my 4 shammies, I did all of Hyjal first (finished at 82.5), then Deepholm until I hit 84 (a quest bugged out as well which prevented me from progressing any further in the zone) then finished off in Twilight highlands.

I had already lvled my prot pally to 85, and I work away so when I finally got to my shammies, the zones were empty. I also did 1 thing to keep the lvling interesting, every time I picked up a collection quest, I did a BG (eots weekend yay :P). I did a LOT of BGs lol. About 50 wins - 3 losses, the xp/hour wasn't too bad.

Also, because I was the only one in resilience (full wrathful) I kinda dominated more than usual, especially at 84.