Lyxen
Great Old One
So one issue with the difficulties area, is what happens with 2x, 3x, 4x type deadly.
These do not exist, and if you need them, you are using the system so much beyond the bounds of the standard system that it should really be up to you to decide how to deal with them. If you deform the system to your ends, you should be able to deform the Encounter system the same way.
Once more, it is supposed to be a simple streamlined system, and that is what made its success. And to stay that way, no system can try and cater for all the variations that people might introduce in it.
But you know what, why don't you try designing something of the kind and let us judge what you did and whether it suits us...
And yes that section can be useful but it doesn't even cover all standard options that are common for players to deal with.
It does not need to. The system is generic and simple enough, just apply the basic principle.
Magic Items of course are a big one, while they are "optional" you certainly see them a lot in the various modules....
No, you don't. Please show us where in the published modules there are a lot of magic items.
so at least some token lip service to them would be expected (aka players have +1 weapons and maybe armor, what does that do....a least the basics).
No, it does not. The game does not need +1 weapons or armor, and there are very few of them in the modules, actually.
Or feats, if I allow feats should I just automatically assume 1 difficulty drop, or is it a half one, or does it not change the difficulty?
And again, please design a simple system yourself where it takes into account the precise difference between Great Weapon Master and Linguist. Exhaustive, if you please, and with differences whether these are taken by a bard or paladin, and taking into account the differences of stats, of course, all the combinations of them.
I respect that a simple system based on CR is not going to be perfect, a simple model will high variance, and a rigorous one would create far more complexity than most are comfortable with. But I can also say having run games for a long time under 3.0,3.5,4e, and now 5e.... that 5e's encounter difficulty estimate is the "worst by far". When I ran deadly encounters in 3.5....my players were sweating. In 5e if I'm not at 2x/3x deadly, its barely a real encounter.
And honestly, I totally dropped it in 3e after a few levels because it was even more variable than 5e, especially between casual and built characters. And the same with the NPCs./Monsters.
4e is different because it is so much controlled, so yes, it was more accurate, but at the cost of openness.
As for 5e, it is incredibly open, and streamlined, but it has consequences. If you choose to use it, deal with it.