I believe the librarian scrolls are bugged. I have tried, repeatedly, every dungeon the internet says they drop in including the keep depths levels 1-3, Battlefield’s Stores, Cryders outpost, Bridge Stores, and underbridge.
And by repeatedly i mean i spent almost 8 hours strait.
So today I finally found them after about 5 or 6 tries, they were in the Battlefield Stores, just as you enter the first level.