What to do with L32 15/14/15 Rhyhorn?
1. No Sinnoh Stones left. My other Rhyhorns are mostly 89% with one 91%.
2. Only Ground attackers are a L30 Groudon (14/13/15), a L30 Rhyperior (15/15/12) and a L30 Rhydon (13/14/14). My three maxed Machamps complete my Heatran team. (I love Gyarados but...Stone Edge.)
3. Rock attackers include two L30 93% Tyranitars (I have spares to power up as necessary) and two L30 91% Golems.
4. 538 Rhyhorn candy. Nearly 2M dust (with many good candidates). Possible future Community Day.
Answers
I'd say evolve it and replace one of the machamp and evolve the rhyhorn, Rhyperior is a superior counter to heatran, will do very well agaisnt thunder dialga sets when it comes to raids, and when the beasts come bak to raids, Rhyperior will do very well against raikou and depending on the weather, partly cloudy or clear, great agaisnt entei
I find rock more useful than ground, in general for gym clearance, and apart from the Heatran raids haven't used the ground Rhyperion as much as the double rock, but for the Heatran raids the ground has been great. I had a 100% and a 98% Rhydon to evolve so those were my first stones (just completed the set of Sinnoh's today).
Both double rock and double ground Rhyperion are very strong for their type, and I don't think you'll regret going with either. Not many players can afford the candy for a full team of smackdown Ttars or Groudon...