I kinda hope aegislash is able to stay in ou. Fun mon to use with a cool concept. Plus all the good counters like hippo and mandi are in and checks like bisharp, excadrill, hydreigon and kinda ttar? Pen can also just sit there and bore him out if he doesn’t have sd lol. Also some new mobs could do a number on him like the impadimp line not being weak to ghost fighting coverage and the new pseudo legendary if he gets that juicy ghost stab. Would be a lot of fun seeing him back in but I doubt it with this power recession.
Hippowdown isn't a counter. No one is a counter. It's the Aegi.
252+ SpA Life Orb Aegislash-Blade Shadow Ball vs. 252 HP / 144 SpD Hippowdon: 227-269 (54 - 64%) -- guaranteed 2HKO after Leftovers recovery
252+ SpA Life Orb Aegislash-Blade Shadow Ball vs. 252 HP / 252+ SpD Hippowdon: 185-218 (44 - 51.9%) -- guaranteed 3HKO after Leftovers recovery
You have to run fully SpD. defensive to have a chance against it, also Shadow Ball has a chance to ruin your SpD. "Oh but that is theorymon" I'd accept that if Aegislash were a new mon, but it isn't, we all know very well how its shenanigans work. King's Shield alone is half the reason for it to be banned, that shit creates SO many 50/50 situations it's not even funny and the worst is we've seen it in real scenarios. It can run Shadow Plate, Physical SD, has priority, pursuit, leftys, abnormal stats in both forms, SpA. sets that hit like a truck...
In fact, no one of the Pokémon you've said can switch in reliably. 3 of them get fuck by Sacred Sword, hippo gets rekt by shadow ball or toxic stall (toxic sub kings...)
252+ SpA Aegislash-Blade Shadow Ball vs. 0 HP / 4 SpD Bisharp: 106-126 (39.1 - 46.4%) -- guaranteed 3HKO
This is without hazards and running leftys. Then Bisharp can do basically 3 things: pursuit, knock off, swords dance. If aegi gets the king's shield in pursuit or knock off GG. Even Tox gets eventually rekt by subs aegi. He cant stand the Shadow Ball spam with potentially SpD drops and scald does shit.