I was in the same boat you are, Baj. Had to level NIN and I hated tanking wiht it. So I did some research on it and found 4 ways to get NIN through the jungles.
1) (tank) Sub WAR, equip as much +eva gear as you can, and blink tank.
2) (tank) Sub WAR, equip as much def gear as you can, and straight-up tank mandies since they don't hit very hard.
3) (DD) Sub RNG, equip a gun and as much +r.acc and r.attk you can.
4) (DD) Sub WAR or RNG, get a ton of shurikens and as much r.acc and r.attk you can.
Personally, I chose #3 and leveled ninja from 26-29 as NIN/RNG with a gun, some pre and some post ranged attack change. Both times, I was top DD in the party over BLMs, MNKs, DRGs, SAMs, and a few other melee DD. Got pretty hard to hit anything after 29, though, as marksmanship is only a B or C class for NIN. It is very possible and rather effective if you equip yourself right and tell parties ahead of time what role you are assuming. My NIN is still 29 but I plan to just bite the bullet and tank the rest of the way to 37. I dont' like using the ninjutsu to hold hate so I plan on using a lot of shurikens.