The gun gave a throaty roar, overpowering the soft gurgling as the creature collapsed to the ground. Flynn wasn't too sure what it was, just that it was like a shaved gorilla with a sharks maw, and it smelled worse than three day old road kill. That was easy enough to ignore though, the fact that a half-dozen rounds from a service pistol only served to piss it off - that was an issue. How fortunate the frantic chase had led them past a mutilated security guard, a shotgun lying close to where the man had fallen.
Chance of rolling 7 or 8 on a d8: 25%
Chance of not rolling a 7 or 8 on 3d8: 42%
Probability of one success on a d6 - one in three
Probability of complete failure to hit with three d6: 28%
Pattern for d4s: 50% and 12%
Why the boring math? Because super shotguns are fun. If you remember a certain game staring a space marine from 1993 or its 1994 sequel -you know what this means. If you don't, you are dead to me - as dead as pinkies, cacodemons, lost souls, and everything else is after a few shots with the BFG-9000...
Dead and Back is a framework for running a game. Most of the time its about survival horror, but that doesn't have to be the case. What matters is how the game master describes the situation, and how often the players are granted respite.
As the above figures show, a one NecroPoint creature has fairly little chance of surviving against an average character with a weapon appropriate to its SDI. As for creatures that are weak but small and hard to hit? Then you can use necrotic threshold to simulate that any weapon can hurt them, but a certain level of success is required to do so.
The base zombies would probably be about two SDI and one NP, Chain-gunners and standard demons same SDI and two NP. Lost souls also have one NP and one SDI, but a threshold of two, so they're really hard to hit.
Our next tier of opponents - like the cacodemon have a higher SDI, but a rocket will still demolish them in one hit, so its still just one or two NP.
Barrons, Cyberdemons, and the like are why there is an abomination category with speed tracks. These are the ones that take many hits, though their danger may vary. Knights have a low SDI, but are still bullet sponges, while their half mechanical counterparts have SDI high enough to take multiple hits from anti-tank weapons.