Every time I have to work with a NI daq device the first thing i need to know is what pins can or cant do something.
Currently this involves looking through something like 7 diffrent documents to find little bits of information and bringing them back to your applicaiton.
A block diagram could easily be a refrence point for the rest of the documentation (you want to know about pin IO for your device look at this document)
Plus a good block diagram can tell you what you need to know quickly, and clearly. A picture is worth 1000 words?
Some might find the current documentation adiquite, but personally i would really like to have a block diagram that represents the internals and capiblities of the pins and device in general. Most Microcontrollers have this and it is an extremly useful tool. So why not have one for the Daq devices as well?