I just went through it as a level 18 - No issues, but it makes sense now, why they delayed it. This issue also could have certainly gotten through testing and all that jazz and then caught at the last minute....provided this is the issue that held it back in the first place.
Not being able to unlock your second Spec class is kinda a big deal.
That being said, until we get a conformation of "The DLC is out, everyone!" or "Yeah, Microsoft accidently released the bugged version" I dunno if people should be downloading this, although from other posts, it seems like MS pulled the plug on it...Did they?
Of course, the fact that it was on the XBL marketplace should have meant that it was a safe, bug free (Well, for the most part, at least) DLC....and we shouldn't have to worry about downloading it for fear of a bug like that.
Who knows WHAT the story really is here? I just hope it's the version they delayed to fix.