Very interesting, WW. I've also seen bathos a far bit recently and had wondered about what 'exactly' it meant. I notice that the Greek etymology (depth) doesn't really seem to fit with the prevailing meaning. Clearly the meaning has wandered somewhat.
The description of your English class reminded me of the classical trilogy of 'persuasive appeals' employed in Greek theatre: logos, pathos and ethos. perhaps one form of bathos is to offset all that serious stuff with a bit of comic relief.