Attributive nouns vs. of-genitive
Simple examples (preferred first, less-preferred second):
The department secretary vs. the secretary of the department.
Fine.
The helpful secretary of the department vs. the helpful department secretary.
No, here you've put the less common one first.
Note, I replaced excellent with helpful, so the phrase would sound natural to my ear. But my answer holds for "excellent" too.
In general, stringing things out with lots of extraneous prepositions comes across as pompous or foreign-sounding.