Haven't seen very much on this so far...
On the Surface it seems like a fairly cheap way to add abilities, with a job and job trait running to 20FP only, and each job having multiple abilities. Adding RNG and RNG trait would give 3 Accuracy Bonuses at L50 for example, WAR would give a defense bonus, an accuracy bonus and Double Attack etc.
It's been reported that subjobs get all the abilities for the mobs level (instead of half the mobs level), and the mobs only seem to get passive traits, not the active ones.
Anyone been doing much experimenting with using Jobs, Subjobs and Traits as a way of cheaply raising abilities?
XI Wiki

