NIN and DRK were first hinted heavily in Syrcus Tower with those named mobs. Red & Blue mage were hinted first in that weird developer meta like quest, before Alisae became a walking advert for RDM.

Dancer was hinted at when Lyse during SB's MSQ mentioned briefly that her sister, the real Yda was a dancer and the dress Lyse wears originally belonged to her. SAM has already been touched on.

The other jobs were never really hinted at, as the dev's wanted to keep some surprises. We haven't had any signs yet for SHB, it's possible there won't be anymore.