Found this info on the Mistmoore page by TukkaYoot and thought it would be helpfull.
The dark librarian spawns at approximately +90, -90, -150, in the "library" marked as 19 on EQAtlas's map. If you go through the double doors and turn right, looking down the hall, it is the first door in front of you.
Ok, first off, I know the spawn has been moved back into Castle Mistmoore to same spawn point as before, room above Advisor on EqAtlas. 3-4 spawns in room. I personally saw the librarian tonight. I timed the spawn and it's roughly 22-25 minutes.only librarian though(just read lower post)
Confirmed. She spawns on the exact opposite side of the monolith as the ***'t librarian. Approximate loc of 17, 2286. Marked on the EQ Atlas map as 8 or "Haunted Shrine"
This mob spawns in The Library marked on this map: http://www.eqatlas.com/mistmooremap.html Her spawn/PH is the mob by the library, the mobs by the chairs don't affect the spawn. She is fairly common, shouldn't be that painful of a camp. Also, she seems to drop the scroll every time.
The Dark Librarian Assistant does not spawn in the same place, she spawns across the way on the 2nd floor, in the 2 rooms right next to the front entrance of the Throne Room. Not the bedroom/bath near the advisor spawn.