Sometimes formalised modelling techniques like UML are not the best solution. Microsoft have recently started talking about “Domain-Specific Languages”, specialised modelling techniques for specific tasks. My Domain-Specific Modelling Techniques page outlines some useful DSLs I have developed or discovered.
Nice article, but you use invalid UML notation in section on Interfaces. In UML, both the calling and called interfaces and specified by different icons. The line joining the two is directed from Caller to Callee. To a person well versed in UML the notation is completely unambiguous.
Additionally, You rightly state that as an Agile Architect you would tailor your designs to your audience. Therefore, it implies that you would not present a UML diagram do business stakeholders. UML is for communication with developers & testers who are expected to be well versed in UML anyway.
So your Statement that some people would misinterpret the notation is wrong, as you would never be presenting UML to business stakeholders.