After the last hotfix changes I can safely say that Castrum currently is dead content. Nobody is trying to do it anymore as Skimishes and CE's will give you coins. The only reason to do it would be for either the memory collectables and the augmentation. Few care about the first and the second has such a low drop rate that it essentially non-existant (30 run, 1 augmentation for a 20 min content that only spawns every 1 hour is not attractive). Add the fact that it neither awards XP nor mettle I can see why this not attractive anymore.
Being in a full instance and only 20 people register of which only 8 show up is pretty frustrating.

They need to fix this quickly or Castrum will die off fast.