Based on the Raven's Purge campaign, this is my understanding of which NPCs are guaranteed to be potential level 3 teachers of magic talents:
Druids:
- Path of Healing: Keldra the Deserving in Pelagia, Rain and Soul in Pelagia
- Path of Shifting Shapes: Merigall, Virelda Bloodbeak, Tarna in Haggler’s House, Merigolene in Eye of the Rose
- Path of Sight: Virelda Bloodbeak, Kalman Rodenfell, Kritre the Caller of Pelagia
- Path of Blood: Zytera, Merigall, Kartorda, Ravil of Pelagia
- Path of Death: Zytera, Merigall, Kartorda, Corpse herder Brenziga of Zytera’s Mogarium
- Path of Signs: Merigall
- Path of Stone: ???
"There's this other good campaign that you could combine with Raven's Purge" is also an acceptable answer.