If you hate leveling NIN, as I usually do, you should utilize Fields of Valor and /DNC if you can. Go heavy on ATK gear and Meat, get Regen, Protect, Reraise (if you want) and start killing. Katanas are pretty decent against mobs that aren't IT. You barely even need to use Shadows also. Throw up 1 set before each fight and ride those, Parry, Evasion and Regen all the way to the end of the battle, rinse and repeat.
NIN tanking Pre-Utsu: Ni isn't all it's cracked up to be anyway. Parties that expect you to solo tank at these levels are stupid and you should leave them quickly.
Also, when soloing, if you start every (every-other) fight with Retsu, you've already put an unbelievably strong Paralyze on the target, helping your shadows last even longer.
/NIN for BRD has a LOT of uses. Honestly, when I used to play BRD during low levels, I'd sing a couple songs for party, Foe Requiem, and then I'd find myself standing around cause my melee wouldn't contribute much and the healer was usually doing okay. /NIN gives you the option of pulling, which benefits your parties more.
FFXI: PUP & SCH
Tera: Warrior mostly