Institutions offer courses for certifications that are in demand. The DCD isnt in as much demand or as popular as the CCIE/MCSE/CCAA/VCP certs. This is the simple reason why no one runs a course for the DCD.
The Design Workshop while not a bad experience, is greatly dependent on the quality of students attending it. If the majority of folks are only vSphere admins, you will not benefit as much as you would've if the majority were architects/SME's. If you intend to cough up your own money for this training, I suggest you not do it. If your employer pays for it, then perhaps you should go.
I dont have any experience with design either and am studying (reading and labbing) whatever I can lay my hands on. I've posted my resources in the thread, Example questions and resources, in this forum. There are dozens of blogs out there from successful DCD candidates that have listed the resources they used. This is TOUGH exam, given the breadth of the blueprint, but certainly not impossible to pass. People said the DCA wasnt easy either, but I poured hours and hours into prepping for it and passed it easily. In fact, I found the DCA easier than most other exams I've taken (and I have about 15 other certs).
I am taking the DCD early August and will post my experience then. Good luck to you too!