If you can generate the intensity necessary to kick your own ass, then even if you're using less weight than you normally would, it's still gonna break you down. I end up using less on shoulders, too (just started DC training ~5 weeks ago), but I do my rest pauses hard enough that I sap every bit of energy out of my delts. I usually throw in a set of laterals at 20 reps right after my last set of presses.
I've been killing myself with DC training and been making gains. It's just a tough thing to do and it's hard to generate the necessary intensity on some bodyparts.