Fantomen: Just to be sure I went and made a quick little test game with a decent communion. It worked!
And I made my first reverse communion ever at the same time.
Il Magno: As far as I know the mod is considered reasonably balanced. It has been played in mp against other mods also considered reasonably balanced and did not seem unreasonable in comparison. I am not sure if it has ever been played in a game without other mod nations though. Personally I would say they are slightly stronger than the average vanilla dom3 nation, but not as strong as the sronger nations. There are a few additions yet to go, so it's possible that may change in the future
I can't quite tell for sure from your post, but have you seen the other warhammer-inspired mods? There are quite a few now, most of them reasonably balanced. Some have even been in a number of MP games with no complaints of overpoweredness that I've heard of.