I don't know about other Worlds, but Walk of Echoes is absolutely dead on Bahamut. I've tried during both NA and JP hours and there doesn't seem to be nearly as many people doing it anymore. (Although this could be attributed to searching on weekdays instead of weekends.)
Searching WoE zone usually only yields 1-2 people in the zone. This is not enough to complete any of the walks effectively.
Its sad to see the dev team develop content that I simply cannot experience (without failing) because there are not enough people doing it. WoE is designed by nature to be a group activity. I do not understand why so few players on Bahamut are not doing WoE anymore.
Therefore, I humbly offer the suggestion that the area have some kind of Cross-World matching. Of course this could potentially create overcrowding issues, but if S-E were to monitor the traffic in WoE and match up certain low-pop servers with others that are frequently doing WoE, then the overcrowding impact would be minimal. More players in zone = more people doing the content.
This may or may not be feasible, but I am looking for solutions. I enjoy doing WoE as something different and refreshing from the day-to-day grind of levelling and doing missions.
In the meanwhile, I will be trying to form WoE parties on a regular basis.