So after a first wave of feedback, here’s the list I have:
(EDIT: latest list may be found here.)
Useful outside of home faction delving (where to find them):
Alderfather (Primal Rift)
Drowned Sailor (Sunken Fleet)
Ethereal Sentry (Hall of Guardians)
Gargoyle (Hall of Guardians)
Grave Seer (Crypt Keepers)
Harpy Mage (Stonesong Eyrie)
King Gobtruffle (Amanithrax)
Luna (The Warrens)
Queen Xochi (Stonesong Eyrie)
The Deep King (Sea of Sorrow)
The Maraji Queen (Sunken Fleet)
Vanya Soulmourn (Silver Necropolis)
Watch Mother (All-Seeing Eye)
Water Elemental (Sunken Fleet)
On the Fence:
Sea Witch (Sea of Sorrow)
Silent Sentinel (Hall of Guardians)
Sledgepaw (Dark Pits)