You could easily level up your crafting ones to suport your battle classes. The is a bit of differences between the gear you craft and the gear you get from dungeons. The reason one may want to craft their own gear is that a crafter can put materia into an item that it can make, to give it extra stats. There's a lot to crafting and how to meld materia and you can find a lot of that info here on the forums.

The easiest route is getting items from bosses and chests in dungeons. To put it in WoW terms, random chests in dungeons can give pink(Wow=green) items, bosses drop green (wow=blue) items...and crafters can make gear that is comparable to blue items, but with adjustable stats.