All the problems with wards mainly come from the gardens and the items in them. Each ward is unique because of gardens and it is most liekely a plague for dynamic server memory. Wards are probably more or less persistent to avoid too many data requests but it make a lot of dynamic memory is kept active.

It is the only reason I see that can explain their system is capable to handle one player in Eureka but they are that limited for housing.

The only solution is to change the system a way that replaces the "real" neighborood by a virtualized one or to make a full instancied system.