No, I don't think that the Ad Comms take the DAT as a 'snapshot". It's an accumulation of knowledge up to that point and a low score either means you did not put in the proper time and effort for you personally to score well, or your education up to this point has not been sufficient to score well. I've heard this same "it's a snapshot" in reference to tests like the ACT and SAT as well, mainly when students don't score well. My take, again, not a snapshot but a more realistic portrayal of your academic level. I'll use an example from high school, our class valedictorian, 4.0 (school did not weight grades) that was very good at gaming the system (school allowed one pass/fail class each term--so she always P/F'd the hardest classes) and she studied 6-8 hours/day, dropped out of all activities so she could devote all of her time to her GPA. When we all started the college search process, she was set on heading off to an Ivy, until she scored a 26 on her ACT. None of us were surprised because she was not a "real" 4.0 student. None of us were surprised either when she got to college, a very good regional private school, and floundered freshman year. Those of us in the top 15% that took chances, challenged ourselves in high school, had realistic GPA's all scored higher than her on the ACT, with most of us scoring 30 or better, and many 33+. Of course we heard, "I just don't test well"...nope, you tested exactly where you should have.
I've heard this from various classmates and on other education boards when I was looking at colleges, "I got a great education, I have all A's". Well, your GPA is pretty meaningless without some kind of standard benchmark to back that up. I know a lot of kids that got all A's, in general classes, no AP's, etc. I'm sure they learned a lot, but that doesn't mean they are going to get a 36 on their ACT.
Doc Toothache's Rankings of schools based on DAT/GPA includes a column for the "Modified SA". Plug your numbers into that and see what you get. I'll go along with I want to go there and say that the DAT is standardized, difficulty of school is relative only to the courses you take and taught by whom. There are hard and easy classes at every college, what you do with that class and the knowledge you take away from that class is more important than the name on your sweatshirt.