I may have located the problem. Before investigating further, it would help to know whether I properly understand how the piano roll view works. I want to make sure I am interpreting the interface in the following picture correctly.
 

The pane to the right depicts the tracks currently being viewed in the piano roll, correct? Thus, I should only see expression data for that track, correct? Either I've completely misunderstood how this aspect of the DAW works, or I have reproduced the problem with a better understanding of what is causing it.
 
Also, for any given soft synth combo track (midi + audio) with midi outputting to the synth and the synth outputting to a stereo audio track, what MIDI channel should events such as CC messages be transmitted on by default?