I don't see ninjas any more different then bards to machinist or red mage to black mage. You have jobs with more support that still bring high or higher dps. What we should instead focus on instead of "nerf this nerf that" is "buff this fix that" because the latter is more of an issue. I think a lot people are looking at ninjas thinking they're OP but in reality they are pretty fluid. Monks are awkward and got nothing exciting. Summoners are super awkward. Black mages are awkward with weird tuning issues. Dragoons do less damage and tether freaks people out. Machinists are on the bottom, clunk everywhere, fits name but not good for gameplay. Heck lets throw in some dark knight in there too for lower mitigation and dps. There's a reason a lot of these are being looked at and instead of trying to nerf your raid party, focus on buffing the rest up instead. (How valuable would TA be if Brotherhood was tuned differently for instance).

On a side note for other tanks: Be gentle to your ninjas and don't whip your bosses around or you'll miss that TA.