Since a lot of the droids haven't been implemented at this point (which I understand as development continues) I'm wondering what the usefulness are for the ones available versus hiring a npc to do the job.
The ups and downs of an economy are similar to the ups and downs of life. They are unavoidable, but what matters is your knowledge to ride the ups and survive the downs.
There are no droids that function as a builder, nor are there pilot NPCs that function as astromech droids. Currently only NPCs can build or produce, and only droids can autopilot. The only current feature I can think of, that droids AND NPCs can do is cybernetic implants. Otherwise, some NPCs work, and some droids work independently.