Texrat, I agree with Sandra on all points.

I would not leave the balance issues of the drums to a mastering engineer - this is a mix issue. It will be very difficult for a mixing engineer to correct a panning issue of just one instrument of a stereo mix. If you try to fix it with a plugin, it's going to do odd stuff with the rest of the instrumentation and arrangement, which to my ears, seems well balanced.

The sparse drum parts in the bridge simply do not fit with the rest of the song which has a fairly rich sounding arrangement. It's at that point when the drum parts shout from the rooftops - " I'm a MIDI drum part! " It would be a shame to leave them as is. Think of adding in some ride cymbals - manually played, where you vary velocity and so forth, to stretch things out between the snare hits - even consider zapping the somewhat random snare hits from that bridge section altogether - you might like it.

It's possible that you have a MIDI controller panning the drums over so far to the left. Could be right at the opening of the song. Have you looked at an event editor to see if there's a pan setting on channel 10?

I do have some comments about the instrumental section - the pad/strings get kind of muddied up down in the low end of things. Also, that section is begging for a solo melody line on guitar. Or a piano solo. Or pedal steel - some kind of solo. Right now, it just kind of hangs there and doesn't do anything.

Just my thoughts.