30 ABY - Church founded, Saber becomes SP, Shadow becomes HP
57 ABY - Divious becomes SP, Praxeum becomes HP
71 ABY - Praxeum becomes SP
83 ABY - Aequitas becomes HP
98 ABY - Crozeus is appointed HP
So currently, Dark Lord Praxeum is the Supreme Prophet and Darth Crozeus is the High Prophet.
They are helped by First, Second, and Third Class Prophets, as well as Dark Seers, and Force Mystics. Then come the extra ranks of Shadow Warrior, Dark Warrior, Librarian, and Chapter Master.
Those rankings help the Church accomplish its duty of forseeing the future and making those visions known through poetic prophecies. However, they do no decipher the messages, merely deliver them.
They also take part in the former mandate of the Alchemists, experimenting and inventing devices and potions to enhance many aspects of a body and its life. As well as Sith Spells.