"It's something that's really not a difficult fix for us and so we're going to implement a patch to resolve the problem. We're fairly certain it'll happen really soon so look out for it." nope
Screen-tearing occurs when more than one frame is shown on the screen at the same time, split unattractively by horizontal seams, as Wikipedia helpfully illustrates. The PlayStation 3 edition is reportedly also affected by tearing but to a far lesser extent.
Darksiders was released earlier this week for Xbox 360 and PlayStation 3 to good reviews, though some rated the 360 edition lower for issues such as the tearing.