Final Fantasy XIV Database - Ffxivpro.com

One thing that bothers me is seeing DRG/NIN. The whole purpose of high and super jump is to erase enmity gained from high damage attacks and even if you did take severe damage from AOE having a mage sub would provide far more support and benefits than /NIN ever would give.

/NIN is situational and works best in no tank situations such as merit parties and whatnot, however, unless you have good reason to need shadows (ie: pulling/tanking) or dual wield (thf, blu, rng, war, etc.) I would recommend capitalizing on supporting the purpose of your main job instead of wasting your sub on a thin layer of unnecessary (read: situational) security.