One of the reasons Registeel is not used in OU is because he is outclassed by Skarmory as a physical wall, who has the precious advantage of having a recovery move, access to Whirlwind and a Ground immunity. That pretty much convinces many people to use Skarmory instead.
As for Rhyperior, yes he has Solid Rock, which is a great ability. but the fact that he's slow, has a 4x weakness to both Water and Grass (3% with Solid Rock), weak to several priority moves and a 45 base Spdef relegated him to UU, where he is more comfortable. And even in UU he's not popular...
But building a team focusing on giving him all the necessary support to reach his maximum potential is possible. Some good partners would be Modest Zapdos, who counters almost every Rhyperior's counters and Blissey who would absorb status-inducing moves that may target Rhyperior. Not to forget Hippowdon, one of the best leads and Sandstorm provider for Rhyperior. Adamant SubDanceRhyperior with 132HP, 192Atk, 168 Spe and 16 SpDef EVs, is the best you can provide this support for. With 404 HP, 400 Atk, 296 Def, Solid Rock, enough speed for Swampert, substitute + Sandstorm SpDef boost, Rhyperior will hit very hard.
Aside from this role, Rhyperior doesn't have a lot of options, Rock Polish didn't achieve much and the bulky set is outclassed by other walls. Not to forget there is no Pokemon in OU Rhyperior can force to switch and almost all of them have at least one supereffective move to deal with him. While Rhyperior requires a lot of support to be effective, it is easier to just pick another Bulky Ground who at least isn't weak to every OU Pokemon.