Why the hell did I choose to leave this group...Rhydon has big problems like crap speed and defensive typing but god can it tank hits O.o I'm going to do my own testing and post some logs
EDIT: I've had some success with a Mono-Attacking set: Rest / Sleep Talk / Rock Slide / Curse, maximum Sp Def investment
Curse spam, then Rest and spam Sleep Talk. When you wake up, you'll be insanely bulky, especially if there's Sandstorm on the field, and if you like you can repeat the process till you're satisfied with your bulk and power. Out of all the STAB moves Rhydon has, nothing is immune to Rock Slide and it has a decent amount of Power, accuracy, and PP. The bulkyness of the set is only helped further due to the constant damage caused by Sandstorm.
Logs (Bolded parts are where Rhydon did stuff, Red parts are where Rhydon owned):
