I'd be curious to hear your load with the 80 ttsx? You chronographed these loads?

I've shot and seen shot a decent pile of whitetail does and pronghorn antelope with 80 grain TTSXs from a 257 Roberts AI, and even more with the 80 grain TSX from the 270 at 3800-3900 fps. The results were essentially the opposite of what you described. Animals were very dead, very quickly.