An audit last year by an independent arm of the U.S. Education Department questioned whether the teaching model of Western Governors University, built around competency-based learning, ran afoul of a federal law. Western Governors begged to differ. Now it has data, in the form of a new survey by Gallup Inc., to make the case that its mentor-based model produces graduates who are more likely to be "thriving" in work and life than are graduates of other colleges.