That's what i call a feature, not a bug. and the article seems to refer primarily to the areas bordering syria, turkey, and northern iran. that leaves a whole slice of iran for fighters to come in through. also, the fact that they've only caught/killed 20 or so hardly heans that that's all there is, unless you assume the army is so efficient that they've caught every single forein fighter trying to enter iraq.
now, even the UN acknowledges the link. from a UN report on nations that are refusing to pursue terrorists: story in the Wash times
Of course, if you read the article you would see that nowhere in it does the UN claim belief that Saddam's Baathists had any real connections or support for Al Qaeda prior to the U.S. invasion. In fact it mentions that it's become a problem AFTER the U.S. invasion. Please not that it mentions postwar Iraq. It also talks about the influence being more widespread. Extracting a quote that kind of supports your theory and ignoring the rest of the article won't hold up.
It would be an excellent feature if we killed them faster than we made them, but since we are fighting the same gang that chased Butch Cassidy ("who are those guys" seems to be a common refrain ), we have no metric on this in the words of Rumsfeld. He also neglected to mention we don't seem to control much of Afghanistan any more, either.