You're only right in one aspect, it's immune to T-wave paralysis.
Everything else you're wrong about, and I was attacking his specific set, not Rhyperior as a wall.
Rhyperior as a wall in OU is...well, really not a wall. It's a physical sweeper with bulk. But to take special hits, it needs Sandstorm up. And in that case, you might as well just use Tyranitar anyway, since it has much better special defense, can boost defenses with Curse, and has a great move pool.
Neither are really walls in the sense Blissey is for special defense. Blissey can do it all. All of the physicals walls are really just bulky Pokemon. They can take 2-3 hits without worrying too much, but will eventually need Wish support, Leech Seed support, etc... to take any more.
Who wants to run the calcs on how his Lonely (-Def) Rhyperior on how many hits it can take from Scarf Heracross' close Combat?
Maybe it's a wall in UU. But in OU, it's easy to take down by any number of Pokemon.