Someone will have to dig up the torrent numbers for AW, but I'm assuming they're grossly high.
And this was probably the crux of the issue in regards to sales.
The game itself was fantastic and reviewed well. But on a personal note, I completed the game over a couple of marathon sessions over a single weekend and after finishing it a second time at the hardest setting, I basically had little reason to go back to the game until the free DLC was released (also fantastic; in many ways topping the main game).
With no online component (thankfully; as it would have simply been tacked on), there was no incentive for habitual game pirates to actually buy a copy, regardless of how good it was.
Despite what some pirates will claim in their defense, most, if not all, really don't care about supporting quality products or the industry unless they are essentially required to do so in order to play (whether it's online services, whatever).