I have a My Book Studio Edition II HDD. Since Mavericks I have the problem, that the HDD never goes in sleep mode when my mac goes in sleep mode. Only when I turn off the Mac the HDD turns also off. Today I have updated to the latest Firmware but this issue isn’t solved.
Thank you John, I will try on weekend. So if see it right, this problem is an Apple problem, not a WD problem. Hopefully Apple will dispatch it with the next OS update.