You're absolutely right.
In fact the reports suck so much, that every one using them on a regular basis will write his own tools.
Here are some possibilities:
1) Reformat the excel sheet by means of a VBA macro within Visio. Launching the macro to be either done manually (convert a selected excel object) or automatically - haven't done this before, but could imagine that the appropriate event could be caught, then the reformating routine started.
2) Export you shape data to excel, then reformat within excel and re-import to Visio.
3) The "King path" (

) - Export the data to Access and profit there from its great report capabilities (grouping, calculations, etc.). For my part, I kept the reports outside the drawings and just attach the PDFs to the drawing. One could however think about pasting images (other other types) of the reports back into Visio.
HTH,
Y.