I think people have 'lolDrg' ingrained into their brains at this point. It's more of stigma than fact that Dragoon is somehow weaker than other DPS jobs, and Dragoon still has one of the higher spike damage Limit Break options if they're fully buffed.

People just choose Ninja because its new, and on paper their skills seem pretty good. In terms of ACTUAL dps though, there isnt' a whole lot of difference between a good Dragoon and a good Ninja.