Cata kind of does have a theme...the Twilight's Hammer is what brings all the different locations together. Wherever you go (at least from 80-85)...there will be Twilight's Hammer. The problem is...The Twilight Cult is incredibly boring!

In BC we were fighting Illidan's Naga/Blood Elves in addition to the Burning Legion's Demons. Obviously that brings a lot of variation and I never felt like I was fighting a certain creature too often.

Then in WotLK we were fighting the undead. It sounds boring because they're only one type of enemy, but in reality there's so much variation within the undead scourge that it wasn't boring at all. I never said "ugh...more undead? COME ON!" when leveling up.

Now in Cata we're fighting the Twilight's Hammer and...that's it. Has there ever been a more boring enemy? They all dress the same. They all basically have the same abilities. In fact 95% of them can be put into one of two categories: warrior or elementalist. By the time I was done with the 80-85 quest experience I was thoroughly sick of the TH, which is an experience I've never had with another enemy type before. I think Blizz really overplayed them in this xpac. They should have come up with some more enemies so that leveling isn't just a blur of hacking through purple robes.