Hi, I'm a current student at Marlboro. I just stumbled onto your post and thought I might give my take. As to the low graduation rate, I think it's important to remember that Marlboro isn't a traditional college. Most of the students that come to Marlboro aren't looking for a fast-track get me in and out program. I know of a lot of people that come to Marlboro and then take a few years off, travel around the world, and then come back. Marlboro is a very rigorous school and it's hard to gage how that's going to affect you until you actually get into the environment. That all being said, that graduation rate is getting better each year. We're getting more applicants and admissions is doing a better job at finding the students that would do well here.
Marlboro is considered a third-tier school for a number of reasons that I believe have nothing to do with the education. The things that U.S. News looks at are odd ways to measure a school like Marlboro. A whole chunk of the ranking has to do with how much of an endowment the school has, how often new buildings are being built, how "selective" admissions is. Due to Marlboro being fairly young and having relatively few alums our endowment isn't anything near Harvard's, we don't have that much reason to build 5 new buildings a year, and Marlboro is really self-selective because of how unique it is. In my opinion (and based on my friends' college experiences) the Princeton review does a much better job of quanitifying specific areas of a college experience. Marlboro is ranked #2 for Best Undergraduate Academic Experience and for something along the lines of great professors.
I hope this clears up any concern. If your daughter has any questions I know there's a prospective student e-mail thingy where interested students can contact current students to ask them all sorts of questions. It's firstname.lastname@example.org
Have a great day!