Make a hypothesis: you want to mix NotePerformer with some libraries you have to run on VSL’s Vienna Ensemble Pro. The reason may be that these libraries are not fully compatible with Dorico in their VST version, while work great as Audio Units. Or you have to make a multi, only possible with VEPRO.
You can do it, and it works great!
In Dorico’s mixer, add an Insert FX, and send NotePerformer’s instrument output to one of VEPRO Audio Inputs. Repeat it on all channels with NotePerformer sounds to be send to VEPRO.
Lower NotePerformer’s internal reverb to zero.
In VEPRO, create an Audio Input channel for each of NotePerformer sounds. Link them, and they will be VEPRO’s mixer channels for NotePerformer.
In VEPRO, add a MIR PRO plugin (either from the VEPRO instance, or as an AU plugin). Send there the NotePerformer sounds. If you want to use different libraries for the same type of sound, use a Bus to send more channels to the same MIR PRO icon.
The result is excellent. The sounds from NotePerfomer become more real, more 3D, with the processing from MIR and the mix with the other sounds.
I don’t know, yet, if NotePerformer and the other libraries play in sync, but so it seems.