Multi crew is awesome. You can get a full crew in minus 30 seconds who are INFINITELY more useful than an NPC can ever dare dream to be. So pretty please stop killing them they were already worthless before this update and now they are even more so.
Erm. Your supposition that NPCs are not useful is wrong though. An NPC in a SLF is like a free huge hardpoint that flies around. NPCs are still very valuable. With multicrew, you still get to use the NPC in a SLF, so not sure why you think this