Alrik is right. Some companies only have to put out a small announcement and the games press will pick the ball up and run with it on their own. Bioware and Blizzard probably lead the pack, there, although certain franchises are likely bigger than any company (I'm thinking The Sims especially, here).
For the smaller companies, though, they have one heck of a hurdle to leap over and that is the general indifference of the games press to small publishers. It CAN be overcome as CDProjekt (Amongst others) proved, but you need to hit them with one heck of a whammy to do so.
All indications are that Larian have turned out one heck of a game, but they are still a small company with the obvious budget limitations that entails. They can't just casually throw a few million into advertising the way EA would, so they have to work on the slow build and hope to create enough interest that their campaign catches fire.
Alrik is certainly right that Germany will be the first and most important market for D2. One only has to look at the German language sections of this forum to see that...