I haven't taken the DAT yet, but I have begun the Destroyer. I agree that it is challenging, but it does cover a wide variety of possible topics.
From reading others' breakdowns, it does seem to be harder than the actual exam, but that may be a good thing.
I make excel spreadsheets with incorrect Destroyer problems. Columns for "Question #, Mistake, What to remember next time"
Know why answers are correct, and what the wrong answers are incorrect. Use school material to brush up on topics.
Goodluck and keep us posted!