I'll just quote that little bit, because the rest of your post is based off that false premise. It counters Sun? Really? Here's a little food for thought:
Timid Venusaur: 252 SpAtk Life Orb Venusaur Giga Drain vs 252 HP/252 SpDef Hippowdon (+SpDef) : 56.43% - 66.43% (easy 2HKO)
Modest Venusaur: 252 SpAtk Life Orb Venusaur (+SpAtk) Giga Drain vs 252 HP/252 SpDef Hippowdon (+SpDef) : 62.14% - 72.86% (easier 2HKO)
Timid Victreebel: 52 SpAtk Life Orb Victreebel Giga Drain vs 252 HP/252 SpDef Hippowdon (+SpDef) : 56.43% - 66.43% (yep, 2HKO)
Sawsbuck: 252 Atk Life Orb Sawsbuck (+Atk) Horn Leech vs 252 HP/0 Def Hippowdon: 60.71% - 71.43% (what a surprise, a 2HKO!)
Essentially, your Hippowdon gets 1 switch into a Chlorophyll sweeper before it dies. That's not a "hard counter" to Sun, that's an easy win for Sun. And against Sun teams with Xatu, Hippo can't even set up rocks like you claim it's so very good at doing. Even Hippowdon's Ice Fang won't deal 50% to Xatu. Sure, Hippo isn't threatened by Dugtrio. So what? It loses to almost every other member of generic BW2 Sun offense. Hippowdon should not be used for the purpose of beating Sun, period.
No it doesn't. The set is Scald/Substitute/Toxic/Rapid Spin. If you have Sub, Toxic, AND Protect, then either a) you lose to SubDisable Gar anyways because you don't have Scald to hit it, or b) you can't spin. Either way, Tenta loses.
Fool. Your arguments are baseless not because of their falsity, but because of their irrelevancy.
Let me ask you this:Does anyone EVER use a chlorophyll sweeper outside of sun? No? Oh yeah, that's because when sun is dead chlorophyll sweepers SUCK. You think it's bad when venusaur has super saiyan four moveslot syndrome? Try it when it can't outspeed anything or boost more than +1 a turn. And it's fire attacks are weaker. And if he carries solarbeam, god forbid... well. As for victreebell and sawsbuck, same thing, except those are not even in OU. so you can't even pretend like people use them in ou outside of sun.
SPdef hippowdon switches directly into ninetales, killing sun. It can't be worn down, because of slack off. It sets up SR, wearing down all of the great fire-types on sun, and even the grass-types.
As for the core of genesect/xatu/ninetales/dugtrio/victini/venusaur, hippow DOES have problems with it, but occasionally he gets an SR up all over genesect's ice beam.
Oh, and he roars wobbuffett. That one takes a teensy bit of prediction, and CAN be a problem. But still, against almost any sun team, hippowdon is the hardest counter you will EVER find.
You're right about darm and victini, people haven't been using them lately so recency bias, but they ARE great on sun. Still, if they u-turn on slowbro, he can't attack on the switch-in, and if they use powerful attacks he's almost forced to slack off. But he does stop them from ruining your team.
They do make you more vulnerable to physical attacks, but less to special. Spdef hippowdon is just a catch-all check to stuff, and a great counter to a lot of other stuff, especially mixed wallbreakers (Grass-knot less nape, for example.)
as for the tentacruel thing, Eh, i forgot about this. Personally i'm not a big fan of subtoxic, but i haven't seen it used enough for it to really piss me off;it might if used intelligently by a couple of good players. Or not.