Do you usually do deads last?
I know when I used to regularly deadlift, I would use 425x2, or 365x6 etc....but that was at the start of the routine. By the end of my back workout, I was lucky to hit 315 for 6.
You're certainly stronger at the start, and should use the big compound lifts when you have the most energy- though if you're up for the challenge/want to shock your body a la Arnold, then doing your routine in reverse can be great!
(Hope I didn't go too far off on a tangent there!)