I do the same, albeit I won't qualify my setup as 'simple'.
I export all my teaching stuff, personal web page and so on from Org files, one file per
course or topic. I export html files, reveal presentations, pdf files for exams or reference documents,
even IPython notebooks (thanks to John Kitchin).
I haven' t found an easy way to rely on ox-publish for subtree publishing
with this scheme where you keep everything in the same Org file.
The problem was with navigation. I use a templating system
where I compute menus and body documents that are inserted in
some html template. So I had to write all the functions that will
do this computation and resolve cross links (not yet perfect in this are).