I don't know if it is only "lag" but it seems not all players get the right calculations to their clients send making the game unplayable in big parties and explored worlds.
You can run bigboi server hardware and will still encounter problems because of the let's say not very good netcoding. The reallocation of enemies occurs at the moment on every configuration we tried (we tried a lot a lot) and on different server.
Serverload and playerlocation does not seem to make a difference because it also happens on noload and stable 13ms ping with no packetloss to the datacenter. I ve done a 24hours mtr trace scan with very good results so it is not the connection.
Running now 4xepic rome@16gb ram on google compute cloud and it still happens that one or more players can't see the enemies, while some are able to see them. Seems like not all get updated or simply desync.