Not many in the gameworld, no. 
While I don’t usually apply the PC stat system to NPCs, I suppose we could say that Thaumatarch Kleitos, who uses so many Talismans he’s barely human anymore, is an INT 7. Ennearchs are by and large INT 5s.
Did you really think I was going to answer that?
Yes. As we get into the late game, there will potentially be a lot of factors leading experienced Theurges to be disillusioned, demoralized, or just desperate enough to join a rebel faction, whatever the rebel leader’s charisma.