That's an amazing answer, I wish it could explain a bit further where is the buried cathedral itself (map shows it's below roshamuul but the mobs seem equally to the corruption on elven courts).
About the rest, there are some discrepancy that simply are unresolved, the ward stones that protected the dream courts, the language used to unlock faceless bane, which race built it and what was their relation (before the corruption) with elves, it shows that we are missing important information about this place, but thank you anyway.