The proficiency to wear heavy armor comes from class or feats. As far as I know there aren't any races or backgrounds that grant heavy armor proficiency. I think only Paladins and Fighters het the HA skill automatically. Everybody else would need medium armor proficiency already and then could take the heavy armor proficiency when they get to pick their next feat.
Life Domain clerics also get HA proficiency automatically.
Shadowheart's old stats seems to be the intended Life cleric default stats.
