Given that Abyssea doesn't 'open up' till 30 you can effective learn your job's role in the time between 1-30. The problem, though, is PLing. People get hand-held from 1-30 and never really learn a thing. Valkurm, Qufim and Yuhtunga are crucibles that, I swear, must be endured if you're to truly get each job's role in the party. We all who endured those zones remember fondly, with great disgust, how much we learned from our parties there. Nowadays, hearing the 'horror' stories of those early parties people want to just 'skip to the end' like XI is some kind of dime novel. I think it's a mistake, personally, and everyone should at least be made to give Valkurm a proper go before doing any other kind of leveling.