So you never actually melted down any motors. I have melted down, by which I mean smoke comes out and the epoxy in the motor is all over the place, multiple motors trying to get everything right for boosted classes. I have also watched others do this.
You probably can get your slightly overheated motors to work like new again with new rotors.
I also have been at several series races with spec 17.5 classes, where there were 20+ 17.5 spec cars, and i have yet to see a motor go up. I honestly think this is not that big a problem.
I do remember guys smoking motors in the early days of BL racing, but a lot of that seemed to be due to LRP TC spec Escs that people didn't realize had timing advance. I never melted a motor with a GTB.