Just a simple search through a card DB shows that these types of characters are infrequent. Baratheon and Greyjoy may have a number of Holy through chapter expansions and there are a few Learned neutral characters in secret of Oldtown. It just seems like Noble and War have been getting more love including more cards that affect that type of crest.
Anyone been building decks that revolve around Holy or Learned crests? I just haven't seen enough of either character type to justify that yet.
Maybe the Secret of Oldtown has more because that chapter pack appears to have a lot of neutral Learned characters.
This post is one of many ways I am trying to learn more about the game and how everyone on here perceives to play it.