We aren't expecting Data Center Visit to impact hunts much because of the additional delay in logging out, requesting the data center transfer, waiting for it to be done, then logging back in. That will make it useless in the case of S ranks (unless someone is going cross data center to try to spawn), and probably not worth the effort in the case of trains when there's likely a train ready to run on the player's home data center.
A CD would be a step backwards in what the visit system was created to accomplish. Players are using world visit for far more than just hunts.
With respect to hunts, world visit isn't really the problem. It's also offered benefits to the community since players are no longer tied to being online at a certain time to join the train. If you miss your world's train, you can always join another world's train. If you play in off peak hours, more players will be attending so the train only takes 30-40 minutes instead of 2 hours.
The problem is how lucrative trains are when it comes to getting clusters, nuts and tomestones. There's no effective limit on how much you can earn in a day or week (outside of the weekly top tier tomestone cap) so there are players that will chain run 7-8 trains a day to gear up alt jobs faster and to make gil, which causes the congestion.
If we were limited to rewards once a day per Rank A, train congestion would reduce considerably because there would be no point in running the additional trains unless someone was farming kills to get their hunt mounts (which is a relatively small percentage of those attending hunts). There would still be the heavy congestion during the first 2-3 weeks of a major patch because a lot more players who normally don't take an interest are trying to farm their gear upgrades and/or clusters for their overmelds but that's nothing new.
It's amazing how many long time members of the hunt community have forgotten the same problems existed even before world visit was added and that some of the things we do now to deal with congestion were tricks we developed to deal with congestion when worlds were still isolated.