Okay. So in the fiction of your game world, things function so differently than they do in our world, and adhere so closely to the mechanics of the game, that it is the only relevant data.
The rules that we apply at the table
must be sufficient to describe the events that they're trying to model, otherwise you would get a different result by using the rules than would actually happen within the game world. If scimitars were better from horseback, then you'd expect a confrontation between two otherwise-identical cavalry soldiers to favor the one with the scimitar over the one with the long-sword. Or even if scimitars are only better for attacking infantry, you'd expect the mounted soldier with the scimitar to outperform the one with the long-sword in that situation.
Going by that logic, the outcome of an interaction would depend on whether or not you're applying the rules or just ad-hoc-ing it, which isn't something that could make sense to anyone within the game world. It's inconsistent, based on factors that only exist outside of their universe.
I don't know if I can view things that way, because I think it makes the characters too aware of the numbers. As if they could look at a wound and say how many HP of damage it caused, and how it could have done a couple more of a stronger sword was used.
If the characters couldn't look at a 7-point wound and a 27-point wound, and tell the difference between them in any meaningful way, then they wouldn't know whether to use a Cure I spell or a Cure III spell. The game becomes almost impossible to play
as a game because your character doesn't have enough information to make meaningful decisions.
Have you ever played in a game where the GM refused to tell you how many HP
you have lost? It's terrible. And if you're playing the healer, then it quickly devolves into a twenty questions game of trying to figure out what the GM
actually means when they describe anything.
Given that most character in most games
can actually determine whether to cast Cure I or Cure III, and when
they are running low on HP, there must be some observable in-game reality which corresponds to HP loss of varying severity. You know, just like in the real world you can (barring complications) generally distinguish between wounds of varying severity.
Granted, the in-game difference between 1d6+2 and 1d8+2 would take a while to observe if you're only relying on personal experience, but you
would quickly figure out that the long-sword
can create a more grievous wound than a scimitar under ideal circumstances. And it would also be obvious, in practice, over the course of several engagements or with a large army. I mean, the average goblin has what? Like five HP? If a long-sword drops a goblin in one go 3/4 of the time, but a scimitar only drops a goblin 1/2 of the time, then you'd figure that out pretty quickly while on a goblin-hunting expedition.
