Level Scaling: I didn't think I'd appreciate it through the entire world, but it's fine. I'm going to be happy to not outlevel every area so fast, at all levels.
What I love is skipping the Cataclysm areas Hyjal, Vashj'ir and Deepholm. I've been through Hyjal so many times because the other two are just painful. I had one single character make it all the way through Vashj'ir and vowed never to send another. I skipped a level 83 Priest and a level 80 Rogue straight to Pandaria. Thank you thank you thank you Blizzard!
A Hunter at level 72 who was already in Northrend could choose between there and Outland. They're both ok, but I've always run right past most of their content via dungeons. The Great Thing here was that I could choose random dungeons for either Burning Crusade or Wrath of the Lich King. I love Burning Crusade dungeons.
That said, my level 83 Shadow Priest was in Throne of Tides last week and it was good, I felt like she contributed really well to the group. Yesterday, the same character in Throne of Tides was with a group that wiped over and over. She felt like she had no dps at all.
My Hunter today in Sethekk Halls was also in a recurringly dead group. Then again, the tank pulled the whole room. Over and over.
Bad luck, or have they been made tougher? I'll run others of other classes and levels too, and we shall see.