Since those of us with this issue have been largely ignored, I'm beginning to guess that relatively few of us have purchased just 2 DLC packs, and thus we can only be matched with folks with the same DLC combo. With that, add in a relatively less-popular match type, and you get 0 matches found.

Thing is, there's NO WAY I'm buying the other DLC packs just to see if it corrects the issue unless Activision/Infinity Ward confirms this is indeed the case and it's not actually a problem on their end.