"and the sample set is large enough, you would -expect- there to be some outliers who mostly got things right, by pure chance."
According to the article, "In fact, she's so good she's been put on a special team with other super forecasters whose predictions are reportedly 30 percent better than intelligence officers with access to actual classified information."
If they mean that after the team was formed, the predictions are still 30% better, than random chance ceases to be an acceptable explanation. If they mean that the team that they formed was 30% better on the predictions used to grant entrance into the team, then your objection still holds. Unfortunately, I don't think the article makes it clear which is the case.
That said, there are definitely some mechanisms that could lead an outside group to higher accuracy on these sorts of things. The two biggest are: 1. The insiders are simply that bad, for whatever reason, and random chance can easily beat them, and 2. The failures of the insiders are correlated and overwhelm their theoretically superior information, and I'd especially finger potential ideological biases there, which could affect both information filtering and the analysis. (It is one thing to believe the world should be a certain way as a result of one's ideology... it is quite another to believe the world must already be a certain way as a result of one's ideology, even when one is staring evidence in the face that it is not. One is noble and laudable... the other somewhat less so.)