Well, I may have answered my own question... In terms of the problem happening on a "stock" install, I had simply deleted all the contents from Gamedata and my save, so I guess it wasn't entirely stock.
I installed a brand new game and the rovers worked fine. I THEN installed half of my 73 mods which again broke the rovers.
I had to delete that install and re-install KSP again fresh. I began copying mods over in groups of 5, and starting KSP each time, a new group of 5 were installed, all the way to the exact half that I had copied over before. I could not get a single mod to break the rovers. After that half got installed, I then started copying over the other half in groups of 10. Still, nothing broke the rovers.
My original save file was lastly copied over and the rovers are still functioning just fine. Mission accomplished.