From what I've been reading about crew skills, it looks like they have almost zero impact on your character.
For a warcraft perspective, I chose JC on my tank because it allows the only way of boosting my primary stat (mastery) over non JC gems/enchants and engineering because it is the only class that has improved or on demand mitigation. Two obvious tank roles.
Of course, there's an awful lot we don't know yet but does anyone else have any thoughts?
From what I understand, as well as gathering and crafting etc, some of the crew skills will help provide alternate paths through the operations.
So instead of fighting through loads of mobs to reach the boss fight, they'll let you take a shortcut. For example, if there is a machine (such as bulldozer or drill) near a wall and someone in the group has a certain level of slicing, that person will be able to activate the machine to knock down the wall for a shortcut.