The jobs are all a type of person (samurai, ninja, warrior, summoner). Gun blade is just the weapon. Some of the base classes are "person who uses X weapon" names (lancer, archer, etc) which would lead to 'gunblader' which is.....yeah. but when you become a full fledged job you are more than 'person who uses this weapon'. Samurai is a class of people. A position. As is a bard, a paladin, etc. What role does a person who wields a gunblade have? Im not really sure. But gun breaker doesnt quite seem to be it.

If they wanted the front line imagery they could have gone with something like Vanguard or something. But i understand they also want to convey something unique to the class. Samurais and ninja have so much cultural knowledge you dont need to tell someone that a samurai uses a katana or a paladin is a sword n board woth holy magic. Theres nothing so universal for gunblades so they are kinda stuck using the gun as the focal point.

Im not really sure what could have been done better. But i dont particularly like what we have.