Personally I think the DAT is useless, minus some of the physiology stuff.
PAT is a measure of how much time you can put in to looking at similar shapes over and over again to find out patterns to quickly "guess" the answer properly. Ask anyone who scored well on the PAT to repeat the PAT again after a few weeks, or months after not "practicing" and their scores will plummet.
QR is useless in the grand scheme.
RC is useful, but I walked in without preparing and got a 21. If you can read, you can read. Not to mention, the passages are "relevant" and "interesting" topics related to science and perhaps even dentistry. If you want to be a dental student, clearly you have the "dedication" and "interest" to read these passages without being distracted.
Sciences for the most part are somewhat relevant. But I'd say things like whether Reptiles came before amphibians is absolutely useless information that has no relevance in dentistry or really any medical setting.
Physiology sure, microbio sure, but knowing about the different biomes and what kind of egg platypi lay? No.
DAT to me is just the SAT all over again. It's nice to know these 2000 vocab words, but chances are you're either going to forget 96% of them or just plain never use that information again.
Also before anyone says I'm just saying these things because I'm salty and couldn't handle retaining all this info, I did well on my DAT. I just tend to see things in terms of "usefulness" and as someone that's been working in the dental field for quite a few years, and have talked to numerous dentists about both dental school and the DAT, the test itself is just a means of showing how much you can process and retain in a short amount of time. It's accurate to gauge how studious someone is, or can be, but it's by no means relevant in terms of content.
Also I'd like to throw one last bit out there. Seeing how someone can go from a 20 -> 18 (example) just because they didn't know the exact year that Dino's went extinct, or which prehistoric era dino's lived in seems kind of "unfair" to me. But I guess that's just the way the world works.