I don't see how it isn't a reason for the paladin to offer himself up. If the NPC won't survive without the paladin's help, and the paladin gets eaten, the NPC dies as well. If we accept that what the paladin did was murder (which, for the record, I don't) then this alternate scenario is a murder-suicide. How is that any better? Because the paladin made a "noble" gesture by dying with the NPC?
Personally, there's nothing noble about such an act. I think that such an act is fundamentally selfish. The sacrificial paladin would rather die with his honor intact than accept dishonor and continue to be a force for good in the world. As I see it, such an individual puts others seeing him as a hero over being an actual hero.
I don't really know what framework you're working with. I'm using one that is found (in various forms, but the differences don't matter I don't think to the current discussion) in mainstream non-consequentiaist moral philosophy, in the criminal law, and in LotR-ish storytelling.
Key to all versions of the framework I'm using is that
particular agency matters. This is related to ideas like
responsibility,
duty,
honour,
excuse, etc.
To take a graphic example: if I am killed defending my child from an assailant, and then my child suffers at the assailant's hands, I am not (posthumously) liable for negligent parenting or child endangerment. If I give my child to the assailant then I am. The fact that my child suffers either way isn't relevant - what the law fastens on is
my conduct.
Likewise in the scenario at issue in this thread: the measure of the paladin's conduct isn't
simply the outcoe it produced. There is no version of paladins that presents them as Benthamites. The measure of a paladin's conduct is
what s/he did by way of honouring duties, respeciting values, etc.
As for the suggestion that it's selfish to follow duty when that results in one's death: what you're saying, in effect, is that honour and duty don't matter. That only outcomes count. That's obviously a tenable position - Peter Singer is probably the best-known contemporary proponent of it. But it can't possibly be reconciled with the idea of a
code or of
personal honour. This becomes obvious if we look at the standard bugbears for act utilitarians, like some cases of torture or punishment of the innocent. But likewise in the current scenario: what is the meaning of a duty to
protect those in one's care if it can be set aside in order to pursue some (so-called) greater good?
And for the sake of clarity: this post is not arguing that utlitarianism if false and the morality of duty true (nor the reverse). That's not what the thread is about and is possibly contrary to board rules. This post is talking about
what paladins believe, by reference to the general archetype of a duty-bound and honourable warrior.