I'd have to hear more about the claims on both sides.
Going simply by the information here, I more or less agree with Blizzard. I do not think a company should be able to copyright something made for another company, or an IP that they do not own (in this case Warcraft). I believe this sets a dangerous precedent for allowing big companies to basically steal other people's IPs or at least their names. If another equally big company wasn't getting involved, I'd be quite worried about this.
Of course, we have yet to really hear Valve's side of the story, and that means a lot. Despite not being a shooter fan, Valve always seemed fairly decent to me despite their poor work ethics (Half Life Episode 3...) and so on.
But then again if you've been paying attention, Valve has been changing a lot in recent years. They've backed down to censors, they've violated promises to fans as far as game support goes... and that was a big part of the "Left 4 Dead 2" contreversy, and other things.
Valve is still the company that gives us a decent discount on games over STEAM a few times a year, but understand that they seem to have also been getting considerably more ruthless and greedy as well in recent years. Like any company they have always been motivated by making a profit, but there are degrees in how people act in pursuit of that goal and how much of a profit people want to squeeze out of things.