So Ninja will get special Mudra "actions" like hand positioning in Naruto, or Runes, or whatever else you want to call them, and using combinations of these will produce different effects (for instance an Aoe ice based "Hyoton" attack, or a single target "Katon" attack, or an AoE enfeebling thunder based "Raiton" and so on)
Now that's a really cool and smart idea

I still think 5 is too small of a number, at least for some jobs (not just Ninja), but I guess we will just have to wait for the level cap increase (expansion) for that ^^