Is it worth to level Crafting/Gathering professions while leveling?

[Iscah]

Also worth noting: in ARR you can complete most MSQ and sidequests as a DoH/DoL (so long as you're at the correct level for the quest) and receive the reward EXP into that class. You don't need to have it equipped the whole time, just for the final step of talking to the person with the green "complete quest" marker.

They 'fixed' this in Heavensward, but it still works for ARR content.

[Avatre]

They 'fixed' this in Heavensward, but it still works for ARR content.

In such a way that you had to be the right classification of job, but could do the quest as a level 70 WAR, and claim the EXP on an appropriately leveled anything else(DoW/DoM).
I still do my moogle quests on CUL(which is the only 70 I have for crafters) and claim the EXP on a sub-60 class.

But with SB, you have to complete the quests as the class you started it as.