Wow Monday? Waiting nearly a week to play something i allready paid. Bad move bethesda, bad move.
Simply trying to make sense of the situation here...
I thought about it and perhaps something with their Microsoft exclusive deal forced their hand so they had to release Dawnguard when they did? Perhaps they realized how buggy Dawnguard is with the X-box beta, but weren't able to delay the release, only get to work fixing it. Wasn't the beta english-exclusive? Perhaps, since the initial Dawnguard release, Bethesda's been hard at work fixing bugs for the PC and PS3 release while trying to find a way to patch/rerlease the Xbox version. As they were busy with that, SURPRISE!! The foreign language ones are completely broken!!
Not defending it, per se, just trying to make sense of releasing a bugged DLC. To my knowledge, and I could be wrong here, but DLC aren't simply patched, but rather have to be re-released entirely, so the patch is essentially downloading the game all over again. Josh Sawyer justified certain workaround fixes in New Vegas (a potentially immersion-breaking terminal to recall all companions, since many people couldn't access Honest Hearts since it required them to dismiss companions, but ED-E had a bad habit of disappearing so you couldn't dismiss him) saying they CAN'T patch DLCs and would have to re-release them. Perhaps this is because Steam and the other networks update games automatically and aren't able to tell which users HAVE Dawnguard and which don't? Shivering Isles had it's own patch, but that was to be manually picked out and installed by the user, not automatically by some network.
If something about their legally binding agreement with Microsoft forced them to release Dawnguard when they did DESPITE their knowledge that it's bugged, then yeah, I'd imagine they've got their work cut out just to fix it and prep it for PC and PS3. That could potentially explain why the sudden multi-culti bugs have taken so long to fix.
Or they're complete idiots with horrible priorities and testing procedures, who knows?

(joking of course)
Again, just trying to make sense of the situation...