How to create block diagrams efficiently?
I've been working professionally as an engineer for over 20 years now and can say that while there is no single dominant application for creating block diagrams, the one I see used more than any other is Visio.  In addition to hardware engineering, the tool is also widely used by network engineers--to the point where companies like Cisco create stencils for it.

The caveat here is that Visio a windows only tool.  Though being that you're BootCamp perhaps that's not a show-stopper.