Thanks for the followup, Sam- it's always nice to get a clearer picture of a problem rather than leaving the next guy hanging.
Odd that they nixed the idea of low-gearing it down a hill, that really seems weird. I know other members of my 4WD club with auto trannies did it, but those were generally older, valve-shifted trannies rather than computer-controlled like the E4OD. Could be that the force-feedback from the driveline and locked TC did cause it to overheat, who knows.