> "Revolver" by The Beatles is a good example - the record is quite uncomfortable to listen to on headphones because tracks are panned hard left or right, creating a completely artificial sound.

The Beatles were only preset for the mono mixing of most of their albums; they were not there for stereo mixes of albums like "Revolver." This probably just reinforces what you're saying, but I would like to think if they were around when the stereo version was mixed there wouldn't be as much hard panning. I believe they mixed "Abbey Road" in stereo and the mixing vastly better.