TL;DR: Spread NA DCs out. The playerbase will naturally distribute itself evenly for better ping so Aether is no longer the PF hub. Nobody is punished and everybody wins.
The Problem - Half-assed solutions to what was a small inconvenience result in new issues and exacerbate the original problem in the long run:
Ever since data center travel was implemented, raiders have gravitated towards Aether in search of a livelier party finder and many players from Dynamis, the newest data center, regularly traveled away for faster duty finder queues. Unfortunately, this mindset of Aether being the raider server and Dynamis being dead was a self-fulfilling prophecy, and so it became difficult for many people to do some activities on their home servers. It wasn't a terrible system because the process of traveling between any data centers was generally quick and easy, but there were some small inconveniences like not having access to retainers or linkshells that many players would endlessly complain about. Square Enix has made attempts to solve this that haven't panned out.
In 7.0, Square Enix temporarily limited data center travel for North American players so that they could only access Dynamis and Materia. This had the benefit of making Dynamis and Materia more active than they have ever been and it worked fine in the interim before the savage patch. However it could never last. You can't introduce a feature like the ability to play on any server in the region and then gut it permanently like that. For example, roleplayers might be able to meet up with their RP partners on Dynamis or Materia, but they would be disappointed if they permanently lost access to RP venues that they spent the last two years socializing in. Although obviously this was only intended as a temporary measure during the new expansion.
With the release of 7.05 they rolled back the 7.0 restrictions and introduced a new system in which servers categorized as "congested" have a drastically reduced capacity for wanderers and travelers. This makes it practically impossible to travel to many servers during most of the day. Even a standard world can become restricted during peak hours for travelers if it is on the same logical data center as a congested world. While it did keep party finder active outside of Aether for the recent savage tier a bit longer than normal, there are some serious long-term concerns to be had about this.