I think you're severely overestimating the increases in damage. Keep in mind that the skill change only brings weapons up to their existing potential, and the specific weapon edits only changed weaker weapons. The largest hits you can take are no larger than they were in vanilla. The only things that are going to one-shot the player are high explosives, and that only if unarmored. Also, as damage goes up and health goes down, each additional health point has increasing marginal value because there's less of a surplus buffer.
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After playing with these changes for a bit, I'll decide if the endurance multiplier needs to go as high as 7 or 8.
7 or 8 would be a lot better.
I wasn't overestimating. I fired this mod up yesterday with the intention to use either it or Arwen's for my next playthrough. I started a character with 9 strength, heavy handed trait and tagged melee and immediately noticed that it still took 6-8 swings at the upper body of a nearby farmer (with a sneak attack critical included at the beginning) to kill him (had this happen with both mod tests). Next, I went over to pete and another farmer, they both had .357 magnums, and they felt a lot more deadly to me than I did to them. This was on normal mode also because I assume that is the ideal setting for a modded game (and because I'd rather not lose the same amount of % damage that I gained through the mod). My character had 7 EN and was wearing the 8 DT vault armor that comes with the classic pack, and I thought to myself, if goodsprings is deadly, how does a high EN character survive at higher levels? So I loaded up my 8 EN (9 with implant) character and immediately noticed that the amount of damage I was taking during the final assault on the fort was way disproportionate to the amount of extra damage I was dealing to the legion centurions and, more than anyone, Lanius.
Don't get me wrong here. I don't mind enemies that hit harder, I actually welcome that. And nor do I expect your mod or any mod to bring damage to call of duty-style levels, because that's not what I want. But I guess my two gripes here are 1.) NPC damage shouldn't be so pronounced against someone with 7-9 EN stat points and 2.) the damage increase should be proportionate to the player's damage as well, whether that damage is melee or ranged. After all, it seems that most people are upset at the bullet sponge feel (outgoing damage) rather than incoming damage, how much they got hit for.
Lastly, don't confuse this feedback as criticism towards you. The vanilla gameplay is so whacked out that despite enjoying FNV's massive story, I just think it'd be a waste of time to play over again on a different path with the same unbalanced mechanics/broken DT rates. I really appreciate all the effort that is being put forth by all the modders here attempting to bring our gameplay back to what we had it in Fallout 3 with mods, and the game's only been out 2 weeks so of course we can't expect things to be ironed out already. But I wanted to post here because the EN issue was the primary reason why I wasn't using the mod. Everything else looks great.