I'd recommend the following in addition to the blueprint (blueprint has a lot of links to other content).
Also my experience here.
I guess it depends on your exposure to design.
If you're coming at the exam from an operational perspective, you may struggle with the "design" aspect of the exam, rather than the technical side of the exam.
For instance, differentiating between functional and non functional requirements. Determining Risks, Requirements, Constraints and Assumptions.
You don't want to spend too much time revising technical aspects and not concentrating on your approach to design.
To that end, i would recommend the VMware vSphere Design books by Scott Lowe as well as the pluralsight course "Designing VMware Infrastructure" or the vBrown Bag Podcast series for the VCAP5-DCD, while the tech has moved on the design methodology still applies.
Dont neglect vSAN or BCDR study either.
These all helped me pass the VCAP6-DCD :-)