Dark Templar only takes medium padding. Has medium armor rating.
Guardian takes heavy padding, is medium armor rated.
Both set chestpieces are 112 armor. Which, I’m pretty sure, is medium rating, not heavy. I think this because the Royal armor set, Flawless, is rated the same as these armors, and the Royal Armor is medium armor by default.
So, either both sets are meant to be heavy, in which the armor rating on both would be wrong because the other medium armors have the same armor rating as BOTH of these, OR there is a heavy and a medium and the armor ratings are wrong for one of them, OR both sets are intended to be medium and the requirement of heavy padding is a mistake for the Guardian set.