Just remember, Ninja was not originally designed to be a tank replacement in XI. The playerbase did that, it surprised the XI devs when they saw how Ninja was being used. Granted, now they've tweaked the job and given them gear and such to improve tanking capabilities. But originally Ninja was meant to be a DD. So even if Ninja isnt designed to be a tank class in XIV, if there's a way for the playerbase to utalize its skills to that end, it'll probably happen anyways.