H Phys WILL help you for the DAT, but if you can't fit it in, it's no big deal. You may even be better off taking an easier courseload and using the extra time to study for the test. Make sure you understand the role of the kidney, digestion, excretion, circulation, and the lymphatic system etc. I studied all these on my own and got a 24 bio, I have yet to take physiology.
If you can't take the class, go through Kaplan or some other study book and use that as your physiology study guide, supplementing it with a textbook.