Not to pile on you PK gaming, but RP landorus is... Well it IS hard to deal with when set up;my whole team can attest to it. On the other hand... Celebi can take a hit and fire back, as can rotom-w and the latis. So it's got plenty of offensive checks. The difference between that and offensive "Sack something" checks are totally different. Normally this here would be a dickish move of "HAHA UR OVERARCHING POINT IS RITE BUT NOT EXAMPLE SUCK IT NUB", except... the example sort of misproves the overarching point. Really, find me a few other pokemon that are generally only checked by a few other pokemon/sacrifice and counter KO. And they can't be easily pursuitable either, because that makes a strategy like this actually feasible.
 
You also bring up haxorus. Let's start with the less bulk, continue on to the ability to run mixed sets and heal, and finish it off with skarmory, which basically counters everything haxorus runs except:
Haxorus in rain(Can still stall for a miss)
SD LO Superpower(And still a beautiful check to that)
Your SD dragon plate taunt bulky set(Did anybody ever use that?).
So yeah, there's a major difference right there. And again, 23 base attack goes a long way-it's nearly the difference between excadrill and sandslash. While there are other contributing factors , that's the difference between banned and I haven't seen in it a month in OU.
 
Basically, any offensive team loses a pokemon, and it doesn't lock itself into outrage. And weather boosts one of its stabs to the point that it demolishes everything. Kyurem-B is not NEARLY as good in sun, because it can't just spam blue flare all day. Meanwhile, dragon/fire is kind of not a bad typing-you're still weak to ground and rock, but you're not weak to ice or fighting and you even resist steel, so no priority bailout except... aqua jet, i suppose.
 
If your entire argument is that you can lose a pokemon, then revenge with a scarfer, and not even because you let said set up, you're wrong. At least kyurem-B has a couple checks that it needs to hit with a coverage move. Reshiram's stabs wreck everything but t-tar, who will be outsped sans scarf, which is pretty rare, and maybe chansey/blissey, who can still be slammed by outrage/pwned in the sun. Reshiram actually fucks over offense hugely, especially with a flame charge/sub set.
 
TL;DR:Most pokemon in the OU metagame cannot force you to sack a pokemon quite so easily; haxorus is a bad example because it's got its own problems, and reshiram is just ridicuous and is only "not so great" in ubers because ubers has pokemon with ridiculous bulk to take its hits and ridiculous strength to dish out comparable hits.