That's all great, but it's your DMing skills coming into play, not how the game is written. In 4e, if I was designing a 5th-level adventure that included Vecna's Very Secret Diary in it (maybe it's in the same room as the MacGuffin) and I want the PC's to have a chance to open it, maybe I'll give picking the lock a hard DC...for 5th level characters. In 5e, that same diary would be a hard DC period. They've got a chance to open it, just as in 4e, but now that DC is a property of the item.
If later on in 4e, I've got a dungeon crawl and I want to have hard locks for the 10th-level party, I'll again use a hard DC. That'll make it harder than opening Vecna's Very Secret Diary. In 5e, that same dungeon crawl might just have locks that have a hard DC in them. Now they're as hard as opening Vecna's Very Secret Diary.
Dude, are you listening to yourself? You've left the reservation entirely. I mean really, you're out in loony toons left field at this point. Anyone who sets "Vecna's Secret Diary" to have a level 5 Hard DC isn't portraying it in fiction as something awesome. They're portraying it as something that persons you would be likely to meet on a daily basis have a decent chance of accomplishing (IE Fallcrest, a town of under 2,000 people has a number of level 5 figures in it, presumably at least one of them has a decent Thievery bonus). So, any complaints you make based on the supposed awesomeness of this Diary, are now completely absurd, null, and void, because it isn't really that tough a task in the grand scheme of things (its a DC22, and 4e DC chart goes up to DC42). Its not uncommon for level 1 PCs to have a +11 Skill Bonus, so while DC22 isn't trivial it is far from depicting something really difficult.
Beyond that how does this work? If you want the 5e PCs to open it, you better have some way for them to be surely able to do so, and a hard DC isn't that way!
As for the whole rest of it, its meaningless, your diary was easy in the grand scheme of things, and is roughly a Medium DC for level 10 PCs. So in fact, while you may cast it in the fiction as some big deal, it just isn't, you're using the math wrong.
What I would suggest if you want some sort of super spiffy McGuffin like this and have it play a part in the level 5 adventure is to have a series of graded DCs. The players can unravel some of the mystery of the item at level 5, like that it IS in fact a diary, and whatever other fact needs to be known in that context. Then the thing can continue to present challenges at higher levels, as the PCs gradually figure out what it is that they actually have.
Even a DC that is high for a 5th level character will be really low for a character of 15th level in 4e. In 5e, these DC's are the same - hard is hard. In 4e, these DC's vary with the level of the character - hard for a 1st level character isn't hard for an 11th level character.
The level 5 hard DC is the level 15 Medium DC. So by advancing a whole tier (IE from village strong guy to one of the greatest warriors of the current age) you have brought the DC for something that a very talented and skilled PC could accomplish about half the time into being something that your average trained or very talented untrained PC can do half the time.
And no, AGAIN, in 5e there is no such thing as 'hard is hard', if you define it that way, then you have to acknowledge that the 4e continuum of DCs from 9 to 42 also forms a range in which some things are 'absolutely hard' and that divining which ones those are is pretty trivial when they are neatly ranked by DC. So in fact 5e's terminology tells you something so trivial that it doesn't even need names attached to it.
The "tradmill" problem that can wreck the feeling of achievement. The issue isn't one lock, it's the comparison between the two challenges (and how similar they are in 4e despite the intervening levels).
Again, this is ridiculous because 4e clearly tells you to advance the fiction by advancing the DCs that are considered 'relevant'. 5e doesn't do any such thing. So a 4e level 5 adventure will have totally different fiction from a level 10 or 20 adventure. Foes that were level 5 relevant will be trivial now at level 10, and your character will deploy a whole different sort of powers at level 20, have a PP and soon an ED. It really is a very different game, notionally. I agree that you'll use the same basic mechanics to run it, but not the same DETAILS. At level 1 you push, at level 10 you daze, at level 20 you stun.
Maybe you would, but there's a lot of folks who would see that and say "Hah, well, I guess these other 23 levels are completely unnecessary. Why did I even need 7? If it's just going to be the same thing with bigger numbers, this number doesn't represent me achieving anything."
But the intent of the Neverwinter thing WAS to be a self-contained 10 level mini-campaign. It wasn't intended to be followed by anything else. I don't know, perhaps they suggested follow-ons? Its possible you could go on and tack on another 5 levels and take on the primordials or something.
I mean, to illustrate with extremity, the DM could just declare that your characters are like unto gods and can kill demon kings on a roll of 4, and you aren't going to feel that accomplished killing demon kings because your ability to do so had nothing to do with anything you did as a player.
Mechanically, you haven't moved the needle. It's crystal clear that the DM just gives you a DC that bears no real relation to the game-world, that is calibrated exactly for your level, and that isn't related to the things you do as a player.
I'm so sick of this balderdash. Everything has significance in 4e just like it does in 5e. If a DC25 signifies something in 5e, then a DC35 (roughly the same point in progression) signifies something equally in 4e. You can keep making up this








story that it doesn't BUT IT DOES, and when you keep doing that it really makes your whole argument just this eye-rolling nonsense.
In 5e, if you want PCs to be succeeding in DCs a reasonable amount of the time then you will set them in some range, I'd say level 1 PCs that will be between a 5 and about a 15. For level 20 PCs that will be maybe more like between a 15 and a 25. In both cases you might now and then set a DC 5 or 10 higher than that to represent something that is both really hard and you don't really care if the PCs pass or not. Presumably, because you want consistent fiction, you will describe these things as appropriate (IE rusty latches, simple keys, well-made locks, cunning locks, evil gnomish locks, the hardest lock in the world, etc.
In 4e you'd use the level 1 Easy/Medium/Hard DC (8/12/19) for level 1 PCs, for stuff. The level 1 locks may be of the rusty latch, simple key, and ordinary lock categories. At level 30 with DCs of 24/32/42 the EASY locks will be made by evil gnomish trapsmiths, and the hard one is a living Far Realms entity that drives you mad as you pick it.
I'm lost as to where the lack of progression is here, or why it would be in any way less than obvious to a GM that a DC42 lock is a totally different beast from a DC8 lock.
The fact that Level 7 is meaningless. The fact that you can do that at level 7 supports that point.
And how is Level 7 more meaningful in 5e? Levels are a meta-game construct, they have NO MEANING in the game. They just represent numerically all the factors in the game that make someone powerful (luck, skill, willpower, toughness, divine protection, etc).
The maths are intolerant. You try hitting the AC of a level 13 monster at level 1 in 4e and tell me how it turns out.
You try hitting a CR 8 monster in 5e at level 1 and let me know how it turns out.
Because they don't need to. They can just let the chips fall as they may. The DM doesn't need to know the outcome going into it - maybe folks die, maybe they get clever, maybe they run away.
The adventure that 5e uses to teach new DMs how to play - Lost Mine of Phandelver - has a CR 8 dragon in an adventure designed for characters of level 1-3 or so. It's better because of that beyond-deadly threat.
Better than what?
Suppose I wanted to put a Dragon in my level 1-3 4e adventure. Oh, wait, Kobold Hall, the intro 4e adventure in the DMG, did that! Now, they made it the weakest dragon in the MM, a baby white dragon, and you CAN beat it (though it isn't easy). It could just as easily have been a young white dragon, which would be basically impossible, maybe a super min/maxed party could have done it, but basically suicide. Maybe that would have been a more interesting adventure, but I'm not really defending WotC's adventure writing chops, which in fact IMHO suck. They are farming out all the 5e adventures, and its a good thing! I wish to hell they'd farmed out the 4e ones.
In 5e, you don't have to make the decision to adjust the difficulty of an encounter. You can just let the players handle the fallout. Maybe they'll handle it quite well! Maybe not. Either way, it'll be interesting!
OK, and 4e has a rule against this? Honestly, read any of the 4th Core adventures. They're stupidly hard, with encounters at level +10 all over the place. You're just expected to either pull off something amazing or die and suck it. 4e does this as easily as any other D&D. There is noplace in the 4e DMG or any other reference that tells DMs to rescale encounters. None at all that I can remember.
The fiction isn't relevant - what's relevant is that the difficulty you're trying to hit hasn't changed. It's the same number, you're just better at it now.
You know your 4th time through a boss fight in Dark Souls? The boss hasn't become any easier, but you're dodging and hitting and getting its rhythm down and you used less estus to get there and you're doing better and maybe you've got it this time okay! You've become better at the game - you're a better legendary undead whatits, a better protagonist, a better hero, a better player. In 5e, that feeling comes from whiffing on svirfneblin at level 1 and solidly hitting giants at level 13. They haven't gotten any harder - your character has just gotten better at hitting.
So, what you're saying is that the only valid way for someone to feel a sense of accomplishment is if they hit more often. That's a pretty darned narrow sensibility there if you ask me. In fact I think this kind of assertion is almost patently absurd.
If your game wants to preserve careful balance, sure.
If your game's got no real problem dropping a CR 8 dragon into a level 3 party, the advice should rather be, "This thing will probably kill people. Have fun."
OK, so drop a level 12 4e dragon into a level 3 party. The result is going to be the same. The idea that somehow 5e has invented some marvelous technique that didn't exist or was somehow not blindingly obvious in 4e again just seems absurd on the face of it. One would have to be daft at a level that would preclude functioning as a DM to fail to be able to do this in either system.
Nor will the result be materially different. In 5e the PCs might get a few hits for insignificant damage, where in 4e they might wiff and just do miss damage with their daily/encounter powers that they will surely toss out on round one, before fleeing, if they are still at positive hit points.