Thanks for all of your answers,

I was pondering about this since I am now taking the time to level all disciple of the land and hand job to level 50 before I begin the Heavensward campaign. So far:

Botanist: 50 - Miner: 50 - Fisherman: 50
Goldsmith: 50 - Alchemist: 50 - Weaver: 41

I have been doing that for about a month and a half now on top of my daily beast tribe quests. I just want to get the best equipment and lots of money at the end of the process. So I was just wondering if there was *ANY* reason I should level up other disciple of war/magic classes.

From your answers, different roles (tank & healer) and fun seems to be the only reasons.