As with all metrics, flaws are obvious.. Heavy emphasis on graduates' salaries puts liberal arts and Midwestern/Southern schools at a heavy disadvantage from the start. Resources, if not normalized, advantages large enrollment schools and elite private universities. Engagement is subjective to begin with, and the way questions are worded and results interpreted is critical to the outcome. Finally, any scale measuring diversity along traditional (racial, socio-economic, gender, etc) lines. will disadvantage a school such as TCU (except, of course, the female percentage of enrollment).
Bottom line -- so what? We already know UT and A&M have resources we can't dream about. We already know that, academically, we're very good but not Rice-level selective. We already know that, unless the criteria include toxic culture and dorkiness, we will be seen as roughly equivalent to SMU and Baylor.
For me, the most obvious differentiator is that which can't be measured -- the quality of our students and leaders and the results we get from the resources we invest in them.
GO FROGS!