Agreed that the language gets in the way of the rule. If you look at the Daily Encounter EP guidelines and compare to the Encounter Difficulty guidelines, its plain to see the way it's built.
I don't doubt (and am not going to check up on) the accuracy of your reverse-engineering, I just don't see it as being as relevant in the context of 5e as I might have in 3.x...
3 Deadly encounters get your Daily XP Budget, as does 6 Hard, 9 Medium and 18 Easy.
So, sure, '6 hard encounters (or the exp equivalent) between long rests' might have been clearer. It certainly would have been more exact. It might also have seemed to encourage no deviation...
And all of that is by RAW. It's there in the book, but everyone see's the anecdote about 6-8 and forgets about what the tables are saying.
The 6-8 piece is also right there in the book, not an anecdote.
But, calling anything in 5e 'RAW' in the sense we used it in the 3.5 era is probably inappropriate given it's design philosophy - not just 'rulings not rules,' but the choice of natural language over jargon, and of mixing fluff & crunch without clear demarcation.
The 6-8 piece of advice is there for newer players and DMs who may not be able to handle Deadly encounters on a regular basis. For skilled players and DMs, and for higher level PCs, Deadly should be the defacto encounter difficulty and using that when traveling or in a dungeon puts serious pressure on the players.
And that's not stated anywhere in the books.
I think it's also putting the cart before the horse, a little. Pacing impacts the effectiveness of the encounter design guidelines, a 'Deadly' encounter is not so deadly if it's the sole encounter of the day, if it follows 8 moderate encounters, it might be quite deadly, indeed.
If you make the possibility of random encounters while resting always of the Deadly sort, you begin to solve the problem, because you aren't gaining anything by resting when you face a deadly encounter and can put real strain on the party if it get's behind this curve.
I don't think that does help, at all. If you know you might risk a deadly encounter by resting, you'll need to factor that in to rest frequency: always rest while you still have the resources to handle a deadly encounter.
I think a 6 man party is a huge change from a 4 man party.
With a party of 4, you either have to kind of fill each of the "classic" four roles, or risk foregoing one of those roles in order to really focus on one. So you can get rid of a highly skilled character like a Rogue in order to add another damage dealer, and so on.
Rogues can deal pretty good damage, and, thanks to backgrounds & BA, skills can be pretty well covered by a party almost regardless of composition.
But if you can simply add another damage dealer without sacrificing a skill class or a caster or healer....then you've significantly altered the core assumptions, I think. My players have 6 PCs among 4 players, and the extra PCs are not always with them. During those times, I've noticed a huge difference in how encounters play out.
There's also just the simple fact that, under BA, numbers tell heavily, so two more on your side is two more, is more than 50% better...
I'm not crazy about the exhaustion rules either, and rarely use them except in real edge cases. But I thought they would be suitable to evoke the feel I wanted while the PCs are on Athas.
Certainly. I just thought I should admit my bias.
Why not? The DMG gives suggestions for alterations to the rest mechanic, the same as they do for many other game elements.
It does, and those modules are presented as alternatives you might flip on or off for a whole campaign. Imagine if, say, the default rules were all DCs are 15, and there were modules in the DMG that gave you the option of setting all DCs to 10 or 20, instead. That's not quite the same thing as "... the DM sets the DC..."
Perhaps. I would say that "undermine" is too strong a term. I think they create the basic mechanic, but don't at all times require that all other aspects of the game must rigidly adhere to and fit with that basic mechanic, knowing it will work for most, and those who find an issue with it have the ability to alter it until it works for them.
No RPG can actually require rigid adherence to its mechanics, and any GM can reach beyond the rules of any RPG. 5e is exceptional in providing DM Empowerment not by merely relying on those facts, nor even by actively encouraging it, but by presenting rules that naturally call for DM judgement as a matter of course.
Some aspects of the game do that more successfully or overtly than others. Since pacing (forcing or deviating from the elephant's 6-8 encounter guidelines), is such a powerful tool, the rules for resting should have been farther over on the invoking-DM-judgement side, like the core resolution mechanic is.