Better Implementation of Resistance to Weapon Damage?

[Pooky the Imp]

There's a fairly well-known issue with 5e in that an awful lot of monsters have Resistance to Bludgeoning, Piercing and Slashing damage from non-Magical weapons.

Thus, the moment the party acquires magical weapons, that rule becomes a waste of ink.

My question is, do you think there's a better way to implement this sort of resistance? Do you think it should exist at all?

For some monsters (e.g. werewolves) you could remove the requirement for magic and say instead that you need silver. But then, unless you say that silver weapons can never be magical, all you need is a magical-silver weapon and you're good on both counts.

So any thoughts on how this sort of rule could be improved to keep it relevant?

[Mastikator]

I do have some ideas, there's no silver bullet, it should be varied.

1) don't give creatures resistance to weapon damage unless it's justified narratively/by the game lore. It makes sense for a wraith as they are ethereal but does it really make sense for a wight?
Another thing here is that you can give vulnerability to silver/adamantine and resistance bypass to magic. So a silvered longsword is better than a +1 longsword when facing many undead.

2) don't give creatures resistance that is bypassed by either silver/adamantine OR magic. Just silver/adamantine, magic does not bypass. A magic weapon should not bypass the werewolf's immunity, only silver matters here. Also give the werewolf resistance to most other forms of damage too, otherwise spell casters just dominate. Better yet, give it vulnerability to silvered weapons!

3) a small number of creatures have resistance based on circumstance, like light level, this is often bypassed by magic, stop that! If darkness makes it resistant to damage then magic weapons do not bypass that! If a creature becomes resistant while standing on grass then magic weapons should not bypass that. The answer should be to change the circumstances, not to just use magic weapons!

4) Some creatures might have resistance to only piercing, slashing or bludgeoning, but not all 3, and magic shouldn't bypass it. This is typically limited to oozes, but others could have similar effects.

5) legendary super monsters that have resistance/immunity to non-magical weapons should not be bypassed by low level magic items. If a demon lord is immune to non-magical weapon damage, then a common or uncommon should not be enough, and rare/very rare should only set it to resistance rather than immunity. Legendary problems require legendary solutions.

[JackPhoenix]

The issue with wanting different stuff to overcome resistances is the so-called "golf bag" problem, where weapon users are forced to carry multiple different weapons to deal with various enemies. Blaster casters face this too (everyone knows fire damage is resisted a lot), but have both easier and harder time to deal with it... easier because casters probably want spells with different damage types ANYWAY, if for no other reason than different AoEs/saves requirements/other reasons, and harder beause, well, because spells known/prepared are a limited resource. Martials have much harder time changing their fighting style/feats/equipment just to fight a specific target)

Vulnerability (as it is written) is not really a great solution, because doubling the damage output of martials will just erase most foes from existence. It would be better if vulnerability was "the creature takes extra XdY damage when it takes Z type damage"