WD MyBook Studio II suddenly empty!

WD External Drives External Drives for Mac
5

I had your same issue, but I was with a Mac mini and Mavericks (but was just starting to think to update to Yosemite: how extensive this but is!)

I could not recover the content, but at least I could recover the drive:

http://community.wd.com/t5/External-Drives-for-Mac/My-Book-Studio-II-failing-SOLVED/td-p/858178

Paolo