Level 2 Rhydon 100IV!!!
Just evolve a level 2 Rhyhorn with 100%IV into Rhydon for the heck of it and got mud slap earthquake! Max out?!?! Leaning towards yes at some point haha
Answers
Just to play devil's advocate maybe hold off, for now. IV will always be important, but maybe with the gym re-work CP won't be as important. In the end if you are using him as a defender, he's kinda like Gary (gym skimmer). If you NEED him as an attacker and have the dust, then go for it! Otherwise regardless of IV / CP I can take down any Rhydon with a 2400 CP eggy in about 15 seconds.
I am not debating how gyms work now. We all know Rhydon sits up super high in gyms then you just use your army of Vapes (which everyone has now) on it and it dies in about 10 seconds. I was just saying, I have a funny feeling that they are going to change this feature. I don’t think CP will be the end all for gym placement anymore. It would be a shame if OP dumped all that dust into something and then Gyro and Rhydon get whats coming because they are both crap defenders, just used by people to outrank others in gyms so they can collect coins. They do not add gym diversity in any region. I play in a water biome where you only get Rhyhorns along the rocky coast (fairly rare mon) and about 30% of all gyms are Rhydons, regardless of the fact that everyone here has an abundance of water mon to take them out.
If Mega Horn became a two-bar move it might become Rhydon's best defensive move.
However, I still think it is really weird that Drill Run is in Pokemon Go but Rhydon doesn't learn it. I'd almost prefer Rhydon swapped Earthquake for Drill Run.
https://pokemongo.gamepress.gg/pokemon-move/drill-run
http://www.serebii.net/attackdex-xy/drillrun.shtml