We continue mulling through the newly released, complete Dark Ascension visual spoiler here with card number 96 of 158:
Thraben Heretic is no Tormod's Crypt or Bojuka Bog and it's not even a Withered Wretch, but it's still very, very good. It's definitely limited in that it can only target creature cards, but at the end of the day it's a 2/2 creature for 2 mana can that has the ability to hose multiple archetypes.
This card wants to be in the sideboard of a human tribal deck. It wants to be high picked in green/white decks in limited, but not quite strong enough for constructed.