This thread was so interesting that I pulled out my DAT score sheet to compare. I got a 21 AA and that was the 97.2 percentile (as of 7/19/12). So that means like 3% of people are getting 21+ AA. That really can't be THAT many people. I'm sure thousands of students get in with <21 AA so you will be fine! For RC, I got a 24 and that was 98.0 percentile so you know not many people are totally acing that part either. I bet a majority of people are probably around 18-20 in most sections, and they do just fine
You also should consider those people who get like 22+ in the sciences but then 16-17 in QR and RC and they still get a 21 or 22 AA, but aren't quite well rounded. I don't think that looks as good compared to just 20s across the board or something similar. That's just my opinion and I don't mean to offend or belittle anyone who is in a situation like that.
Regardless, if you can make the rest of your application look great by filling it with extracurriculars/shadowing/good letters of rec, etc. then you can do it! Don't sweat it!