I'm gonna have to agree with this topic, it is strange that Paladins get their power over an oath opposed to a deity. From what I remember from the classic games, Paladins always served under a deity and would come across them within different religious temples.
Keldorn from classic BG2 for example served under "The Most Noble Order of the Radiant Heart", Torm, Tyr and Helm are the deities whom the knights in the order follow.
So Paladins do serve under a deity. Only problem here is Minthara, she is a paladin that abandoned Lolth and there is no way she gains her power from the absolute or Orin for that matter. Only fix here would be to make her an oath breaker, but the problem with that is she already has dialogue stating her vengeance oath.
