Interesting concept. Bit convoluted, and it took me a minute to figure out what role it was supposed to be. Still some stuff missing too such as armor type and maybe some ideas for the ongoing questlines for it, but otherwise not too bad.

That being said, my biggest issue is with the lore component. Although the Twelve are deities and there are tales in the game of them in reference to their quarrel with man, it doesn't look like it fits very well when you factor in that the Twelve only shared six elements with each other, and light and dark weren't among them. In that sense, given the references to various deities from specific job storylines or deities that could be compared to specific jobs in the game, the lore of this Archangel concept doesn't quite feel like it fits very well. That's just my opinion on the matter though, and I'm sure there's probably someone with more of an expertise on the in-game lore to find some more suitable way of this concept fitting on some level or another.

As for the whole "scythe as a weapon" argument, the best way of making it look practical while making it look like a scythe would be to make it look more like a giant fishhook. That way, it'd be a lot more of a balanced weapon (which was why normal scythes were never used).