The problem with upholding the core principle of "everyone in a single world" is that not everyone is near the server and this game needs <200ms latency to be playable in PvE and nevermind PvP at that latency, which in turn means the game isn't even playable in many locations - which is exactly what multiple servers solves. Those players aren't going to be in your world regardless, because they simply wont (can't) play at all. I think it's a really backwards logic that they're applying to this principle and it sucks because I'd love to play the game and maybe even PVP. They state it as a core strength, but from the eyes of someone who isn't near that server it's illogical as it prevents us from enjoying the game altogether.
Again, there's no latency compensation, the server doesn't take any consideration from the client which is usually the right way to do it for an MMO (fully authoritative), however games like FFXIV use compensation and it makes a huge difference. Yeah, there's the question of 'hackers' however because it's compensation it wouldn't be possible to be fully adjusted to your benefit, and FFXIV had a lot of issues with security (bots) because it was hacked together as quickly as possible when they made it, they didn't code any security features yet for actual content it works without hackers abusing it. I'm not saying Albion should go this route, I'm only saying that they need to compromise in some aspect so people can actually play their game without relocating physically.
In one of the AMA links the dev says "you can easily play it well with pings as high as 150." - We are >250ms while the server is under load, and never <220ms. Many ability from weak PvE enemies can't be dodged unless you predict the ability. It makes me sad that they say they have no intention of solving these issues.
It doesn't matter what means is used to accomplish having a connection to the server near to you so long as there is a way to play with tolerable latency. Clusters are a great way to do that while keeping the single world, however you mention that they had done it in the past, for the record it is very much technically feasible to do however if the foundation of their server/net code doesn't support it then it can become technically challenging but never infeasible (I have some game dev experience).