"In the hands of a skilled practitioner, thaumaturgy can be a force of terrifying destruction. At the heart of this school of magic lies the ability to call forth and command the latent aether within oneself through deep introspection.
To then mold that aether into sorcery, the thaumaturge makes use of a scepter or staff, within which is housed a medium—a natural stone imbued with magical properties. The guild is centered at the Arrzaneth Ossuary in Ul’dah, within whose hallowed halls are said to reside powers of life, death, and the beyond."
White Mages were never a "force of terrifying destruction" but, like someone said above, while the Arrzaneth Ossuary is a place of worship to the god of the dead, the second temple is a place to worship the living. White Mages' are healers so they are associated with both the dead and the living.
"Conjury calls upon elemental forces present in nature and concentrates them to a potency at which spells can be weaved. Through practiced meditation on the essences of creation, conjurers draw forth and absorb aether from their immediate surroundings. A wand or cane made from unworked wood is then utilized to focus the aether until it manifests as the desired spell. The seat of the Conjurers’ Guild lies at the Stillglade Fane in Gridania, where the voices of Eorzea’s elementals are said to be most powerful."
Again, Black Mages never created anything but, they do call for the elements in nature. Remember, war is imminent and the people of Eorzea may need to resort to different measures.
I also hope that there will eventually be a SMN class. I have two ways that this could be implemented. . .
1. Once you have both BLM and WHM at a high enough rank you could unlock a quest which would unlock SMN.
2. Or, something like this could happen: CON --> BLM --> something, THM --> WHM --> SMN.