I find professions more fun to do as you're levelling, because it's more like 'a task' when you're 70. Plus it's handy to be able to use the stuff that you're making, even if it's only an occasional set of items.

I do:
character1: mining + skinning
character2: leatherworking+enchanting
character3: engineering+blacksmithing
character4: nothing

atm I don't level engineering actively, because I need the ore for blacksmithing