I just took the DAT yesterday and going into it I was not worried about QR, I have always been good at math and I've practiced and felt that I was good on time. But I was so tired by the time the QR section came up and I felt like I was going really slow. Most (80%) of my problems were longish word problems. By the time that I had about 20 minutes left I was on problem #15 and I knew I was not going to be able to finish on time! I ended up scoring a 17 in this section but I skipped the more lengthy problems, tried to answer the easier ones first and in the end had to guess on the last 5 because I had about a minute left!
So it is all about timing in my opinion, and staying alert after the reading section!