I can probably count on two hands the number of gut or gill hooked fish I have had on a Ned rig, don't know how many Ned rig bass I have caught, but it's easily over a thousand. Plus the ones I've seen caught on it by people fishing with me. It just doesn't happen. I can't explain it, you'd think they would swallow that little bait down, but they don't. I use almost exclusively cut Zinkers and Dave's heads with a #2 hook.
C-rigs, Texas rigs, jerk baits, crankbaits - now those are lures and methods where I have problems with them swallowing it.
I don't fish the Ned rig because of the low hooking mortality, I fish it because it just flat out works sometimes better than anything else I could fish.
We're all going to kill some fish just by catching them, we just should all try and minimize the mortality by doing the best we can to minimize hook damage and take care of them as best we can when we put them in a livewell.