I have been testing the AX10 Scorpion Punisher shafts along with the R2 HD version tranny for a while now, and they have held up great, and done their job well. I even tested with my big Holmes Hobbies Hyperion Brushless motor, which has been known to eat parts for lunch, and the Punishers and R2 HD took the abuse with no issues

, which I can't say about the stock drivelines, or even the ones I replaced them with

.
The gears in the R2HD are almost twice as thick as the standard R2, and they are bigger diameter as well, and configured differently for a better reduction, with the same overall gear ratio. My opinion is, they will be very tough to break.
The Punishers are just plain stout, and up to the task of serious crawling.
Good job RC4WD
A couple of pics from one of my test sessions showing my AX10.