Mike, I think you're missing the point. The fact that the performances are not going to be 100% identical is exactly what makes it sound like a real chorus. Let's say you have a group of four backup singers singing a part in unison. If they are good singers, they will phrase together, and the performance will sound tight. Maybe a conductor will even be utilized to help. But they will not be 100% in unison on their vibratos, cut-offs, accents, and other articulations. This is what makes it sound real. And what makes it sound good.
You can argue that it is too difficult to resing a part, but you are flying in the face of history - from the Beatles to your favorite pop artist of today. When you hear four Jennifer Lopez's singing the chorus of a song, that IS her singing the song four times.
Admittedly, it helps if you are a pro singer, because you want the phrasing to be as close as possible. But it will never be 100%, and that's a good thing.
Now, there ARE performances, like jazz improvisations, that really can't be duplicated. In those cases usually double tracking is probably not the sound you want anyway. But if you want to chorus a burning jazz solo, that would be the time to try some electronic tricks. BUT IT STILL WON'T SOUND AS GOOD as if you really played it twice. Check out the "Supersax plays Bird" for the sound of four-part saxophone renditions of Charlie Parker solos played in real time to hear the difference.
My point was not that you can record a second pass in less time than it takes to copy and paste. My point was that the copy and paste will never sound as good as a second pass, even if you have an Eventide Harmonizer etc. to help make the pasted vocal "different" with detuning etc. Since even if you spend hours with high end processors and fx it will never sound as good as having the vocalist just sing the damn thing a second time, then you are hardly "overprocessing". If anything, you aren't processing enough since your results remain inferior.
By the way, I won't be around much this week-end, so maybe we should wait until Dragon's new screaming server is up and running to continue this discussion...
Meanwhile, HAPPY THANKSGIVING all!