Not sure if this is a bug or if by design, but if it’s the latter, I haven’t been able to figure it out what the point is. So before submitting an issue I thought I’d bring it up here.
When adding a VCA fader to MIDI tracks (and I’m really glad this actually works – would love to see support for VCA type adjustment of continuous controllers as well), the MIDI tracks that contain no volume automation stay at the same volume. This is the behavior I would expect.
However, if the MIDI tracks happen to contain automation, the reference point is actually mapped to +6dB on the VCA fader, not 0dB. This leads to the MIDI volume on all those tracks immediately dropping.
See animated GIF for illustration: http://dl.dropbox.com/u/8520185/cubase8_vca_midi.gif
Only workaround I can figure out is that if you have any MIDI volume automation in the session, then you need to create automation points for all MIDI tracks and add any VCA faders mapped to MIDI tracks directly at +6dB and work from there.