I think many of them weren't on Aether at that time and didn't have to deal with the constant crashing of the DC we had happening. That would be my concern with combining anything. They seem to have found a sweet spot with 8 per DC.
I genuinely cannot think of a single issue it wouldn't solve, the core reason people DC travel is to PF and for roulettes, with that fixed, everyone would just stay at home, save for things like meeting up for Maps and Hunts. I occasionally hear people whine about things like "DC culture" and such, but people who act like that are pathetic and not to be taken serious.
I don't disagree with the idea but also there is more issues that a cross-DC PF would fix, like Aether(and whatever are the raiding DCs for EU and JP) congestion in the first few weeks following Savage release for example, cross-DF would just be a side effect of that, because PF uses DF to begin with to actually join instances, so it would be just a bonus.
I would not be surprised if the state of Dynamis did in fact at least have some impact on Square-Enix speeding up the rate at which they added Trusts to the game (including adding them to a few trials later on) because they realized people were literally getting stuck and needed more warm bodies, even NPC ones, to progress.
As well, the RP scene DOES tend to fancy more modern attire if modding is anything to go by, and Dynamis in particular had more modern themed venues compared to Crystal... so it's vaguely possible that too could have influenced some of Square-Enix's choices in cosmetic aesthetics post-Dynamis launch which just-so-happens to include Dawntrail.
Oh, and of course we can't ignore the effect "dynamis" has had on the story I suppose. Wasn't that the writer's excuse for Wuk Lamat being so stronk out of nowhere at certain points in the plot?
You know... I'm starting to see why some people may have developed a visceral reaction to the "D word" if they've subconsciously associated it with "everything that's bad" about the game right now.
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Removing DC travel at this point would all but ensure the death of Dynamis, not be its salvation, and I can only assume the people who keep suggesting to shut it off forever as a "solution" are those on Aether/Primal/Crystal who would not be affected at all by Dynamis being isolated and left to rot away.
We already have proof that closing the gates even temporarily did not bolster activity by much with the Dawntrail lockdown, and in fact played a part in the first "exodus" from Dynamis as people refused to be trapped there again. The second exodus was caused because there literally wasn't enough people to successfully do content that was world locked, with the lowest populated Dynamis worlds (including my poor Maduin) seeing an influx of people leaving. I can personally attest to seeing dozens of people, mostly gatherers and crafters, disappearing overnight as "unable to retrieve information" and then seeing them forever labeled as being on another world a couple of days later, indicating a transfer had taken place.
Then there's the more obvious Materia which is even deader than Dynamis and its kept its players trapped there day one. Shuttering DC travel would not save Dynamis, at most it would only bolster the health of Aether/Primal/Crystal as raiders and RPers are forced to stay on their original home worlds, and that's assuming they don't just transfer out anyway or even quit over it, and the game really doesn't need to be giving more people a reason to leave.
My theory is Wuk Lamat speed running her growth in strength and reliability was supposed to show how good the WoL is as a mentor and so the devs could push the idea that a future generation in a post-Hydaelyn world could absolutely be as jacked as the WoL is and the world would always be in safe hands. ("Look to those that cane before to lead those that come after.") But, yeah, she went from zero to one hundred in like 4 levels of alpaca wrangling and watching Krile cook that it didn't hit like they wanted.
I'm forever salty those challenges weren't minigames or instances of some kind after the Pelu Pelu one hinted that each was going to have a little gimmick to play with.
But anyway. Dead or near dead servers.
Holy shit, I completely forgot Materia even existed. If the game were available in South Asian countries that would be a great place for them to congregate outside of Japan's datacenters, but I had assumed that was the audience the flagging Mobile remake was meant to court. Oh dear.