Quote Originally Posted by YanderePrincess View Post
Conceptually, maybe, but in practicality, they don't. They're int-based spells. Rog/Nin is a melee dps, most likely str-based, possibly dex-based. Just like if you could cross-classed Aero or Blizzard II onto a Lancer or Pugilist, you won't get any significant damage out of it.
Classes/Jobs have varying INT stats, Ninja could have a higher INT stat. Cross-class skills are rarely as potent when not used by there originating disciple. Normally skills are modified by traits, but just overall less damage could function similarly. Furthermore, we don't rightly know if Ninja wouldn't be a step toward hybrid jobs which draw their damage output from not only attack power but also magic attack power. Going only from how the game works currently is thinking in a rather limited scope, and assumes no evolution down the line.