Honestly, the guys (and pretty lady) from Larian know what they're doing. I'm sure they've done all they can short of tv-commercials and gigantic promotion stunts. Look at the buzz the Witcher generated before it came out. Wasn't that great really. It was mostly due to its quality that its sales took off big time. And that's what we have to hope for in Divinity 2. As for me, I'll do a lot of word-of-mouth publicity in my area... Hope there's a collector's edition, too.
And really, it's a no-brainer that there was little publicity between 2005-2008. It was the same thing with Dragon Age, and that's as high-profile as it gets. It just doesn't pay to do something, because generating buzz 3 years before something hits the shelves may hurt your game more than it benefits it.