You seem to be arguing that the existence of one bad diagram and one (related) good text explanation proves that, in general, needing a diagram is bad, and being able to explain something succinctly and clearly in text proves the merit of the thing being explained.
I...do not feel that this follows in any way, either as an absolute or as a rule of thumb.
In my personal opinion as a user, usage of WiX is extremely complicated (requiring multiple different tools, thousands of lines of XML, understanding of the incomprehensible MSI database format as well as the multiple levels of inscrutable macro substitution WiX puts on top of it, and so on). The documentation presents a diagram of the 11 different tools involved (which I'm not saying is a "bad diagram").
Usage of WiX-sharp (which wraps and hides the mess decribed above) is so simple that a complete sample project is just a few lines of code, as shown in the README. There is no diagram because none is needed.
This is consistent with (but doesn't prove as a general rule) the idea that "if something is so complicated it can only be understood with a picture, it's too complicated"
I...do not feel that this follows in any way, either as an absolute or as a rule of thumb.