I'm happy for this retest as it was nearly not banned last time (and under current voting policies would not have been; it's why you're not allowed to change your vote now after posting lol) so it's certainly borderline enough to warrant a second look.
If I am recalling correctly, I used Aegislash on every XY team I built. It's really, really good. I think people overstate its power though. You basically have to run the fast Life Orb set to have a chance to beat many of its checks, and while that set is strong, we're not dealing with DPP Salamence here:
252 SpA Life Orb Aegislash-Blade Shadow Ball vs. 248 HP / 192+ SpD Heatran: 138-164 (35.8 - 42.5%) -- 90.9% chance to 3HKO after Leftovers recovery
Heatran runs Speed now, making the attack hit harder but forcing a switch immediately to over getting OHKOed. Also, as much as I love such a set, it forfeits much of Aegislash's defensive utility, which is supposedly its "healthy" effect on the metagame.
The slower sets with Spooky Plate or Leftovers hit decently hard, but these simply cannot break past defensive Pokemon like Heatran, Zapdos, Gliscor (SDef), Venusaur-Mega, Sableye-Mega (SDef), Amoonguss, and even some Hippowdon. (Mandibuzz too if you consider it relevant.) It's not like it's without offensive checks either: either Landorus forme, either Mega Charizard, Excadrill, and especially Bisharp are very annoying Pokemon for it to face, and the forfeiture of momentum to them is a very real issue. It's not like the Zards are wallflowers or something.
Its versatility is very frustrating and it has a ton of soft checks but many fewer hard checks. I don't think "oh it can Head Smash Mandibuzz!!1!" is a very good argument, but it can pick off a huge number of its checks. SD is particularly threatening, and SubToxic is very annoying if you pack the wrong checks.
King's Shield is very annoying. I personally don't see this as a problem though. If Knock Off and Scald are allowed, which actually much safer to spam (as you *can* lose the 50/50, which can potentially be devastating, so there is a natural deterrent for spamming KS). As part of the whole package on a Pokemon, it's one of its most compelling traits, but I think to ban it based on this mechanic would be flawed. It's not like physical attackers aren't buffed enough in this meta.
My only hope is that people approach this test with an open mind.
Look, a lot of good players disagreed on it last time. It almost didn't get banned. This doesn't mean anything in itself (hashtag appeal to popularity), but when you look closer, it speaks to the fact that it's not so egregiously broken that it got rolled out of the tier like Greninja or Mawile did. It's not as threatening. Conversely, this Pokemon is buffed to the max, which is why it was banned in the first place. It's kind of hard to say exactly how good it will be in this meta, though some effects are more predictable than others ("yay my offense doesn't lose a Pokemon to Gardevoir every time it comes in"), but whether that effect is healthy and whether Aegislash's strength can be contained remains to be seen.
Bring on the madness. Definitely getting reqs for this one.
As one final postscript, I feel like this is the retest Latias never got in DPP. During the initial Aegisalsh test I spammed this comparison, and I suspect it still holds up. How do we tier a Pokemon who might be individually broken and over-centralizing, but whose impact on the tier we might actually find positive? It's an interesting question.
