Don't use Destroyer as a measure of your score. Use it strictly as a learning tool. If you've already gone through it 2-3 times, however, and are still getting a bunch wrong, then I would start worrying.
Destroyer is a tool for learning. Do not compare it to the real DAT. It is better to learn using tougher questions, but be fully prepared.
Some people who said Destroyer and Topcscore were too tough, but scored in the teens. DAT varies, you can get easier or tougher versions.