Levelling to 90 is still important, notably for those profession alts (although with 3-item restriction, it's not as much important as it used to be).
Most of my prof alts in Cata and MoP got fed their components, got their skills to 525/600, then, when I had time, I got them leveled. It worked, since you could get profession even not fully leveled for the expansion. For most, I simply leveled using archeology; all deposits in vanilla lands give full gathering XP with rested XP bonus, and if a mob decide to pick on you, it dies instantly and horribly. It's fast and competitive with questing, which I'm usually fed up with when levelling my engineer (usually the last profession alt).
In WoD, that simply does not work. None of the trainers offer your 700 skill unlock; you actually have to go to Draenor and kill mobs to get your professions unlocked, since apparently you need to get a random scroll drop for everything. The alternative involve building your garrison to level 2 (which require quest line to be followed), which unlock all your buildings, which apparently offer training at last. So that means levelling to 92 asap, including at least unlocking the garrison.
(disclaimer: I'm not in beta, I'm just reading the various profession guides around)
So, gearing up is not important, being 90 is.