Re. "directivity": Did you use the actual Instrument Profile for the violin, or just a General Purpose profile?
In any case: We put enormous efforts in measuring the actual frequency dispersion patterns of most instruments used for the original Vienna Instruments back then (... we even developed a new measurement system for the task). If you already find MIR's behaviour "counterintuitive", it would be interesting to get your reactions to some of these directivity profiles. :-D
-> https://www.vsl.info/en/manuals/mir-pro/think-mir#instrument-directivity-profiles
Kind regards,
/Dietz - Vienna Symphonic Library