Robot, you misinterpret "forcing balance to run fighting priority" as "forcing Fighting-type Pokemon to run fighting priority." If I responded to the rest, this argument would be circular.
He's still got a point though. No team archetype is running Fighting priority purely or even primarily for Cloyster over other threats like Hydreigon and Bisharp. I suspect you knew this, and refusing to respond to the rest of his post accordingly seems like pedantry to me.
Anyways, support Gengar being raised to A-, why does this Pokemon always get slept on? Gengar loves the slower SS metagame and Specs all-out-attacker just shits on most balances while not being completely deadweight against HO. I've been using double Ghost cores with Gengar + Aegislash or Gengar + Dragapult and you legit just shit on most teams once you chip their Mandi or whatever Ghost resist they've got.
Cloyster's a definite threat but I'm not sold on it being like B material, I'd rather see it start somewhere in the Cs and move up if time warrants it.
Aegislash is legit kinda broken lol, not sure even A+ does this thing justice, I'd say there's a reasonably solid argument for Aegislash being in S but I can't be fucked to make it.