However, it seems that with the new July update, the tank position may once again veering towards the hands of the ninja thanks to the job enhancement spotlight falling on the assassins from the east. July will be adding the new job ability "Yonin," which will increase a Ninja's enmity (hate gain, for other MMO players), critical strike rating, ninjutsu tool use and evasion, but lower their accuracy. Sounds like a tanking ability to us! (Except for perhaps that accuracy down part, but we'll look past that for now.)
The job will also grab the new ability "Innin," which drops their enmity and evasion but raises their critical strike, accuracy, and damage dealt with ninjutsu tools. Lastly, there's a fix going on the Ninja two hour cooldown ability, Mijin Gakure, which will allow the ninja to come back with 50% health and no weakness state after they sacrifice themselves by using this ability.
Interested in the full run down of the abilities? Check out the Final Fantasy XI website for all of the details of this job update.