Summoner hands down and no questions asked. My memory is fuzzy but if I recall correctly no other job in the game touches any of the subjects of the main story.

We found out during this expansion that the story from Dragoon from 30 to 50 would have a part to play but the job story from 50 to 60 does nothing for the main story.

The same thing might happen with Monk for the next expansion if we end up going to Ala Mhigo.

It would be really good story telling if the level 50 Dark Knight story mixed in with the main story somehow.