If anything, I feel the statistics you've provided here are a reason why Aegislash should be welcomed back to OU. Yes, being in the tier does mean that mons have to use more coverage and can't cover everything in two moves anymore (never understood why people complained about Aegi ruining Terrakion, since even with dual STAB EQ it could do whatever it wanted with the last slot).
If Aegislash was truly this borked mon, and a glue that makes any other glue outclassed, it would have been sitting at a way higher rate than its XY peak of 29%. To me, that shows that Aegi isn't as powerful as some users have been implying. 71% of teams found 6 mons they wanted to use over it, or better suited to a certain role. Whilst I know useage doesn't equal viability, I think we'd have seen more Aegi if he was as flawless as people are making out.
I take those statistics to mean that Aegislash is a powerful and high tier mon, but not to the extent that it is mandatory to build a successful team. Some mons require more coverage and as such have more answers, and in return we have one more mon in the tier that is a centralising but by no means an overwhelming force. The trade off to me is worth it.
At the same time, how much can we confirm about what those 71% of teams were running?
Aegislash is so versatile and influential in the Meta that failing to prepare extensively for him can auto-lose even moreso than the current team Match-Up issues people discuss would entail. Failing to pack multiple checks to Garchomp did not mean auto-losing to 27% of teams. However, it is feasible to believe lacking appropriate checks to the opposing Aegislash set meant losing to 20-29% of teams in XY, because Aegislash was ridiculously potent at blocking offensive threats or breaking whatever specific threat a team's sweepers/wallbreakers needed removed.
Aegislash didn't need to break anything like 40% usage; the fact that he could show up on a team and instantly invalidate a mon's effectiveness if he was made several mons drop out of viability. Garchomp and Lando-T force you to play carefully if you have some mons weak to them, but it's significantly less likely to make an entire team weak to them compared to a team weak to Aegislash.
Also, the Terrakion argument is a perfect example of what that one moveslot can cost a mon. Terrakion's Gen 5 sets consisted of
- Banded
- Scarfed
- Double Dance
- Sashed Lead
- SubSD
All 5 of these sets take a hit with Aegislash around.
- Choice Sets outright forfeit all momentum to an Aegislash the moment they click anything besides EQ,
252 Atk Choice Band Terrakion Earthquake vs. 252 HP / 0 Def Aegislash-Shield: 228-270 (70.3 - 83.3%) -- guaranteed 2HKO after Leftovers recovery
Which Aegislash could potentially tank, leaving Terrakion locked into a move with an EXTREMLY exploitable immunity
- Lead took a hit in general with Defog, but losing Taunt severely worsens its match-up against opposing leads like Garchomp
- And the Boosting sets were outright unusable since those depended on Terrakion having 2 free moveslots
So a Pokemon ranked A+ in Gen 5 for set variety lost 2 sets, had 2 more take a severe hit, and the last one still had Aegislash as a contributor amongst negative factors. Granted, Terrakion's been on decline even after Aegislash left, but that's still a very dramatic impact for Terrakion, who DID have moveslots to spare. Now consider others like Pinsir or Heracross, who outright had to give-up otherwise superior options (Close Combat) to avoid being walled and exploited by the sword.
Jirachi, Celebi, and Starmie (All A ranked or higher) fell off, the former 2 offering no defensive synergy that Aegislash didn't while lacking other supportive options to make them still worth choosing over it, the latter inhibited in its main job and forced into a very precarious position to try and still do it. To ramble off some other things taking a severe hit: Breloom, Dragonite, Alakazam (Normal and Mega), alongside the obviously noted examples like the Latis and the Mega Wallbreakers.
Aegislash doesn't have to be on every team in order to centralize the metagame. Being as common as he was then made him a threat that had to be considered, and when considering him, you realize half the Pokemon currently OU end up deadweight against 20% of teams without anti-Aegislash support.
I'm not convinced Aegislash is going to make Teambuilding fun or less. It just seems like the Meta would go from "who's more prepared for the opponent's team and strategy" to "who's more prepared for the opponent's Aegislash and his merry band of sidekicks". It's no less possible to lose because at that point it comes down to which side is better equipped to deal with the opposing Aegislash, who's more prepared to break the glue holding the opposing team together.
There is very little in the game that is not inhibited in some way by the presence of Aegislash, since even checks to some of hits sets are free turns for other ones. The only mons that immediately come to mind as better in a Slash meta are Bisharp (playing around SS) and Landorus-I (Slash eliminates a lot of his checks/counters, whether directly in battle or by tanking their usage and viability), and I'm not sure we're at a point where we want the latter to be even better than it is without a partner like that.
Also can we stop talking about the old aegi/ meta. Play the new ladder then pass judgment. Things have changed... Goth is used less, pinsir is used less, Landis are still rampant, new megas exist etc. Its a different world so the same arguments don't necessarily apply.
Goth is used less because Aegislash not only destroys Psychics, but because he's a defensive Glue for stall teams already that is immune to trapping, which breaks Goth's biggest niche in dismantling Stall cores. Pinsir was already taking a hit in ORAS, seeing less usage than he did in XY, so I don't find the lack of him that surprising, but Aegislash would be the last nail in the coffin for him. Why would the Landi's drop off, when it's already been established that Aegislash is barely an obstacle to the two and makes an extremely powerful partner to I? The entire reason Aegislash was chosen for this suspect again is because he beats most of the new Megas, so their existence is a benefit since it gives him even more to block when "considering" him for your team. More to the point, Megas aren't the most splashable mons, if only because you only get one of them per team, so that's still serious centralization right there.
And the last thing I will say, having played both the current Meta a bit and the Aegislash meta, is that I just think ORAS right now is more enjoyable than I found the last Meta with Aegislash. Yes, there's a ridiculous number of threats to prepare for, but part of the fun I have is pulling from a huge pool of options and seeing how many things I can cover at once. Teambuilding is as much of a skill as prediction and strategy in battle, and assuming you're sufficiently good at either, proficiency in one mitigates the other to a degree.
When Aegislash was around, I just got bored after a while because every team I built started to feel samey after a while. Yes, the matches were much less reliant on team matchup, but I just got bored of using teams that just lacked variety and not having enough viable pieces to experiment with different builds. After a while, I kept watching dicussions, but I just didn't find myself playing anymore.
Aegislash hampers the ability of the metagame to evolve or innovate, because the tools he's given make it much easier for him to adapt to new threats than for the metagame to adapt to him. Aegislash was initially famous for the Crumbler set, which certainly proved effective: people found Mandibuzz and Chesnaught could answer that, Aegislash simply begins using Flash Cannon, 2 counters handled; mixed Hippowdon proves a problem, Aegislash gets his new SubToxic set, another option down. Unlike most top threats, a typical cycle of:
- "New Counter to Top Mon appears"
- "Top Threat adapts to new counter"
- Repeat
Found more roadblocks at the first step than the second with Aegislash, who narrowed the list of potential options by traits independent of his set, and then further narrowed them as more sets came into experimentation. Keldeo's SubCM set was an adaptation to Stall and Balance finding answers to his Choice sets, but unlike Aegislash, the two sets usually have a very different LIST of answers, compared to Aegislash whose actions shuffle around or even simply narrow the very few answers he already has (SubToxic handled most of his problem mons, only trading off Bisharp and Mega Venusaur).