As someone who is playing a lot on private servers and has even played a catalclysm pserver recently, it always kinda amazes me how people think that cata was so drastically different than wotlk.
Wotlk and Cata felt and played VERY similarly. In fact, all expansions since TBC follow the same pattern/formula and only really classes have changed a lot. But Wotlk and Cata are VERY similar. In fact, Wotlk is much more similar to Cata than it is to TBC, believe it or not.