Only one third (even less so after Delenn) of the ruling council are from the religious caste. So net really theocratic.
I would argue that while not a de-jure religious bodies, the warrior caste and arguably the worker caste can still be viewed as a part of a theocratic oligarchy.
While praying is the role of the religious caste, from what we have seen the military caste is also centered around faith and rituals.
It is, in my opinion, more similar to a militant holy order than to a military junta.
We have seen less of the workers, but from what we have seen they also abide by the Minbari religion and rituals.
For the ethos of the Minbari civilization I would choose : Spiritualist, Collectivist, Xenophobe.
Of course, different pops would have different ethoses.
Warrior: Militarist, Spiritualist, Xenophobe
Religious: Fanatic Spiritualist, Collectivist
Worker: Spiritualist, Collectivist, and either another pick in Collectivist or Pacifist