After Taric's rework I bet he will be connected to Lucian's order.

Lucian himself uses magical stone-ish weapons with holy light energy. We know that Taric was placed in the Demacian faction on the official site way back when. It's only logical that he will be part of the same Demacian order as Lucian is. His rework in progress, I bet that's where he'll be placed in the world.