Reign of Chaos is an awesome title. «Reign» is a the exercise of complete rule, and «chaos» is well... disorder. It is very fitting, come to think of it, if we have in mind the game's plot.
For once, the greatest enemy (or, if you want to be accurate, the tools the Great Enemy, the Burning Legion, utilizes) are the Undead and not the Orcs. Then a Prince, an heir to the throne, slaughtering his own people, sailing to forsaken lands and sinking ships of his own kingdom as a mean to achieve vengeance for his pride, and then turning to the very thing he fought. Then, both Orcs and Humans risking the lives of their people following the words of a prophet seen by most as a madman and eventually discarding old hatreds to stand together against a greater threat. And Ashenvale... will it ever stand to see a similar chaos?
I think the title refers to that, there's no big mystery here. Just because the abbreviation is read «rock» doesn't mean it has to do with the Blackrock. On top of that, as someone pointed out already, they didn't play an important role in Warcraft III. It was nice to start the Human Campaign fighting them, though. It brought back the feeling from the older Warcraft games while not limiting the Human Campaign to a single theme: first the orcish uprisings, then the mysterious plague and the sinister force behind it.
