Yes Rhyperior has his good qualities, but in my opinion, solid rock just isn't enough to shield Rhyperior from that terrible 400% weakness to both Grass and Water. You shouldn't be trying to do that. Those probably help balance it from preventing it from being TOO impenetrable, especially under sandstorm. With a sandstorm user Rhyperior could work seeing as how most grass and water attacks (barring waterfall) are special, and his physical defenses are good however, you have to consider that first of all, the 2 users of sand stream are also weak to Grass and Water which could be bad for your team, and make your team 1 dimensional. Tyranitar's special boost from sandstorm could help, and both are different types to Rhyperior. This may be your most viable point, however, but it works pretty well. You just have to ensure the rest of your team can make up for it.
Also, popular pokemon, especially when they're meant to have bulldozing capabilities don't usually have hands down counters. Rhyperior has all bulky waters (Vaporeon, Milotic, Suicune and especially Swampert) to worry about, and although it's not seen very often, Torterra, due to it's typing walls Rhyperior completely unless Rhyperior has Megahorn. Or avalanche. And other than that, Rhyperior doesn't have that many counters. You've got to be fair on it, considering it's ridiculous physical stats and HP as it is, which without these weaknesses would likely make it uber.
Rhyperior has good Defensive and offensive stats (both in the physical department) a great ability and a fairly good movepool. However, it just doesn't have the Speed Not everything needs to be faster than everything else. You're comparing it to Swampert who isn't exactly an olympic runner either, and he can't learn Rock Polish to correct this problem. And there is such a thing as a bulky sweeper, they don't all need to be fast ones. to really put holes in teams since most teams pack at least 5 moves that pack super effective hits on Rhyperior (Grass, Water, Ice, Earth and Fighting) You could say that about ALOT of Pokemon, not just Rhyperior. Any decent balanced team should be able to cover almost every type, if not all of them. and While the Rock and Ground combination provides fantastic tpye coverage, it destroys it defensively to the point where it's hard for even a great ability like Solid Rock to Save it. BL may be an understatement but that is where it belongs. Rhyperior is way too easily countered and is inferior to Swampert to what it does. Swampert works too differently for it to be fair to compare it to him as well. Rhyperior is not a bulky water, off cours Swampert fills that role better. Swampert can't hit nearly as hard, and doesn't take certain attacks as well as Rhyperior can either.