1. Engineering diagrams, explaining concepts to other engineers who are using the diagram as a jumping off point to deeper explorations
2. "Business" diagrams - the sort of thing we want to see in a Medium article or presentation. The style and correct placement matters far more than engineering.
The first is very amenable to markdown style production - often we want to spend no more than a few minutes creating the diagram. We get (60?) 80% of the way there with 20% effort.
But with every markdown approach I have tried the remaining 20% is flat out days of work. There is almost always a need to place that box there and have this one below and to the right and dammit the layout engine will not agree.
What I would ideally like is a combo - markdown to get me most of the way there, and then drop into some vector format that lets me tweak.