To reiterate, current skillsets are a poor argument because they're all getting shuffled around and changed come 1.20 anyways. Lore is already well established, so it's a more concrete foundation to base theories on.
Even with that said, going the skill route, BLM has always been defined by its elemental magics (all of which CON posesses) rather than "dark" magics. Skills are unclear in regards to job definitions right now, which is why it'll be clearer once 1.20 rolls around.
