The number of people per zone is an arbitrary limitation. TOR already has sharding technology, and each shard can hold ~120 people. Even then, the communication channels are wide open, and shards can be moved between.
While an LFG system would be necessary to sort the chaos, a server-locked LFG system still does no good if there are no people to use the system.
Those games don't have a thinly spread population but they're still using an outdated model. They're doing well with their systems, yes, but MMOs as a whole would be moving in the right direction to throw
They don't need to do anything. They would be much better off, but they don't need to do a thing- they can piddle along with a small pool of subscribers as long as they want. I'm just someone commenting on the internet, too- Hopefully they have someone on the inside who has a better mental map of where MMOs as a whole are going to move in the future.
Also, I wouldn't have much trouble finding the same people constantly. Oceanic primetime is good like that. Having people occur more frequently in your travels is a matter of weighting, and it wouldn't be hard to develop a system to encourage repeat appearances on the part of other players.