Hey, I'm one of the people behind Fiddle.md. I think your example works very well, what do you feel is missing?
I'm using it today for a sales document, it's sweet.
Well, there are some more complex yUML diagrams on the yUML samples page that don't work. It's probably yUML's fault because the syntax isn't quite "proper". But it would be nice if fiddle.md had a way of embedding yUML DSL. E.g.
==== yUML Class Diagram ==== [Company]<>->[User] [Company]<>->[Record] [User]-.-[note: A regular user] ==== end ====