For the last couple of years, I have seen many so-called “architecture” diagrams including those suffering from inconsistent notation, unclear depiction lack of information and ambiguity.
The worst scenario was in my last role, where I dealt with company-wide application integration. Each and every team had their own way to draw (or not to draw) security architectures. Guidelines? Nope. Nervous breakdowns n a daily base if something went wrong? Definitely.
So he/she who’s name is not known created a quite comprehensive PDF guideline which helps you to draw more precise security related architectural diagrams. Definitely worth a look.