The midi channel ‘vu’ meter shows the note velocity I think, so if you’re velocities are low then the ‘vu’ meter is low.
One thing I use a lot instead of the midi fader (apart from automating the VSTi audio channel fader) is the velocity adjustment parameters, for example I set this to 20 for a given midi part or for the track in general and a velocity of 20 is added to all notes for the part or track. Of course, this doesn’t always mean volume, but rather harder playing which is sometimes just what I need for banging out a harder edge during the chorus say on a piano.
Another thing on the midi fader values is that IIRC they go from ‘off’->0->127. So, when you drag it down to off it goes through zero, sends CC07=0 and hence you get no volume. I think you can type ‘off’ into the value field and it jumps straight to off without sending a CC07 value to the instrument (or maybe it’s off->1->128, can’t remember now!).
Mike.