SMN Disease based spells

[Kotemon]

BLM is Fire, Lightning based magic.
<snip>...Come to think of it...are there ANY Dark based spells players can cast?

You forgot Ice.

One can argue about whether or not Bio is a Dark element spell based on various past games. One can also argue in game that Salted Earth, Power Slash and most of Dark Knight is actually based or infused Dark elements despite all being labeled as unaspected. My theory as to why is probably so many things that should be an element are non elemental is probably due to how elemental damage is handled (or not) in game.

[Sevyrr]

My theory as to why is probably so many things that should be an element are non elemental is probably due to how elemental damage is handled (or not) in game.

This is something I've often pondered when looking at the skills and spells available to blm and smn.
And, often in-hand with the above thinking, I've wondered why monsters and bosses don't have elemental weaknesses so ever-present in console FF games (and most RPGs, too).
What immediately comes to mind, however, is the design choice to prevent having "flavour of the month" skill tree builds, such as fire mage etc.

[Jonnycbad]

After 1.0 they nixed Elemental Damage (as well as gear having unique stats i.e. "Enhances Jump Damage" on Gae Bolg, "Additional Effect: Fire Damage" on Ifrit Primal Weapons.
What's odd though is they kept elemental damage in the flavor text, despite it being worthless. Also the auras of the element remain intact when casting magic.