Aegislash is S material, because there's little that can come into a 150 Sp.Atk STAB Shadow Ball. It's Tanky, powerful, has a STAB priority, has a protect move that harshly lowers your attack. Can run an effective Weakness Policy set, and in general is just a pokemon that can be put onto any team. It 2HKOs just about everything with Shadow Ball, and has incredible synergy with Rotom-W. Also, all the examples you've given can't OHKO Aegislash:
0 Atk Hippowdon Earthquake vs. 252 HP / 0 Def Aegislash-B: 168-200 (51.85 - 61.72%) -- 96.88% chance to 2HKO
100 Atk Landorus-T Earthquake vs. 252 HP / 0 Def Aegislash-B: 224-266 (69.13 - 82.09%) -- guaranteed 2HKO
252+ Atk Landorus-T Earthquake vs. 252 HP / 0 Def Aegislash-B: 212-252 (65.43 - 77.77%) -- guaranteed 2HKO
Hell, I can continue:
252 Atk Garchomp Earthquake vs. 252 HP / 0 Def Aegislash-B: 230-272 (70.98 - 83.95%) -- guaranteed 2HKO
252 SpA Genesect Flamethrower vs. 252 HP / 0 SpD Aegislash-B: 248-294 (76.54 - 90.74%) -- guaranteed 2HKO (Not that hard to avoid the +1 sp.atk. You just have to lower your iv in def. by 1 for Genesect to get a +1 in atk)
For starters you know something is wrong with your calcs when 100 attack Lando-T does more then 252+ Attack Lando-T
If it uses Shadow Sneak it will be in Blade form, and Hippowdon is slower then a negative nature aegislash.
Also, I did my calcs on Landorus and the ground types with a
Specs, so it will be locked in and too slow to clean up. If its not Speced, plenty will be able to come in.
4 Atk Hippowdon Earthquake vs. 252 HP / 0 Def Aegislash-Blade: 414-488 (127.7 - 150.6%) -- guaranteed OHKO
252+ SpA Life Orb Aegislash-Blade Shadow Ball vs. 252 HP / 0 SpD Landorus-T: 251-296 (65.7 - 77.4%) -- guaranteed 2HKO after Leftovers recovery
-1 252 Atk Life Orb Aegislash-Blade Shadow Sneak vs. 252 HP / 252+ Def Landorus-T: 51-60 (13.3 - 15.7%) -- possibly the worst move ever
Thats with the benefit of the doubt of maxed attack, Sp.A and Life Orb ^^^ Zygrade will be able to tank both, not going to bother calcing.
The ones I brought up were just to show how weak its Shadow Sneak was, allowing it to be easily revenged killed.
252 SpA Genesect Flamethrower vs. 252 HP / 4 SpD Aegislash-Shield: 132-156 (40.7 - 48.1%) -- guaranteed 3HKO after Leftovers recovery
Good enough to finish off a weakened one. Especially if it is a Weakness Policy one, because then you know it will be weakened.
So, I believe Aegislash should go
down from a
S to an A+