According to VGChartz, combines sales on 360, PS3 and PC for Darksiders 2 so far is about half a million dollars. Now, they're not super accurate, but I'm certain that, yeah, that title is nowhere near selling all the 1.4 million units it shipped.
Darksiders 2 went up against some stiff competition. Sleeping Dogs, Transformers 2, Last Story... and then XCOM and Dishonored came out shortly thereafter. The first game came out in January, against practically nothing. This one... this one had it's work cut out for it. And THQ, despite a strong ad campaign in my opinion, with some decent ads, is no Electronic Arts, Ubi Soft or Activision. Best Buy wasn't talking up Darksiders 2. Nor was Wal-Mart. Gamestop wasn't talking it up, either. Now, I loathe those stupid machinima ads Gamestop runs, but I'm certain that stupid, mainstream gamers are pretty much ONLY informed by whatever Gamestop tells them to buy every season. Which is why only the same 4-5 annualized franchises seem to sell well every year. It's depressing.
Hopefully DS2 moves briskly over the next few weeks. Like for Christmas? That's when I'll pick it up (hoping for some good Black Friday deals). Or maybe the Nintendo Wii U version will sell pretty well. I'm sure this game deserves a bump in sales.
Hang in there THQ. Building a franchise takes a lot of support. Look at Sony; they've been taking a beating for supporting games like Infamous and Modnation Racers. But it's the right thing to do, so long as the game is good.