SE why??

[Nutz]

Changing class is not an option, you would obtain the upgrade for another job's weapon.

I think he means specifically for the myth farming. I've been doing my MNK's weapon, but all of the atma and a lot of the myth farming has been done on BLM.

EIDT: Beaten, but kinda funny that I've been doing exactly what's 'not an option', though it's just a coincidence. I had BLM leveled already.