Well, StarCraft II is in some parts looking to be almost like "practice" for an RPG. According to the Single Player Demo Video, between RTS missions you basically do the same thing you did between planets in Knights of the Old Republic. Hang out on your space-ship and talk to the people there, complete with dialogue trees!
Anyway, I think the thing about WarCraft III was that it was an RTS game but driven by an RPG story with RPG elements. It felt like an RPG, but it didn't have enough RPG stuff to support that, basically making it not worth playing, and the RTS elements barely even appeared in the campaigns. Besides, in StarCraft you got to fight every faction in every campaign. That was one of the things that bothered me in WarCraft III. As humans, I never got to fight the Night Elves, and only a rabble of orcs who didn't have a proper base. Nor did I get to fight other humans. I never really got to explore the races in the campaigns.