One question: Are you sure that the soft-proofing works as it should?
When I open a wide gamut test chart, output profile sRGB and switch on soft-proofing and gamut-indicator, I get a lot of grey fields showing the colours that the proof profile cannot indicate.
But when I switch to another output profile, e. g. ECI-RGB v2, the grey fields should change in some way in comparison to sRGB, but anything stays the same.
RT seems to indicate the gamut control independent of the image output profile, but the output profile is essential for the colours in the image and if they can be displayed by the printer.
Edit: Soft-proofing colour profile was ISOcoated_v2_300_eci in both cases.
Edit 2: I made a new topic out of this: