The idea that it's 'subjective' and the DC slides with the PC's level is false & pernicious.
If, by "false and pernicious", you mean
one of the strongest and most central elements of the system, then we agree. Otherwise not. (I also don't know what you mean by "slides". DCs don't slide in any way I can see; they are
set by the GM.
From the DMG (pp 41, 42, 61, 64, 65, 73, 159):
For your own adventures, use the Difficulty Class and Damage by Level table on page 42 . . .
If a character tries an action that might fail, use a check to resolve it. To do that, you need to know what kind of check it is and what the DC is. . . . Consult the Difficulty Class and Damage by Level table below, and set the DC according to whether you think the task should be easy, hard, or somewhere in between. . . .
Challenging terrain requires a skill check or ability check to cross. . . . Use the Skill Check Difficulty Class table below to select a relevant DC for the party’s level. . . .
When terrain requires a skill check or ability check, use the Difficulty Class by Level table (page 42) to set a DC that’s appropriate to the characters’ level. . . .
Improvised Terrain Effects: The D&D game would become a bloated mess if we tried to cover every possible obstacle or terrain. If you want to use something not covered in this chapter, refer to the examples here as a guideline. . . . Is there a chance that a character could try to enter a space and fail? If so, ask for an appropriate check. . . . Use the Difficulty Class by Level table (page 42) to aid you. . . .
Set a level for the [skill] challenge and DCs for the checks involved. As a starting point, set the level of the challenge to the level of the party, and use moderate DCs for the skill checks (see the Difficulty Class and Damage by Level table on page 42). . . .
When designing your own environmental dangers, rely on the Difficulty Class and Damage by Level table (page 42) and your common sense.
And from the Rules Compendium (p 126):
The Dungeon Master can use the suggested DC for a task or set one using the Difficulty Class by Level table. The table provides DCs at each level for three categories of difficulty: easy, moderate, and hard. When choosing a DC from the table, the Dungeon Master should use the level of the creature performing the check, unless otherwise noted.
In other words, across the lifetime of the edition, the DC by level table has been at the heart of setting DCs. (For combat DCs - ie enemy defences - instead of the DC-by-level table there is the monster design table in the DMG, in conjunction with the guidance on what level range of creatures is suitable for an encounter. The function of these guidelines is the same as the DC by level table.)
To my mind, the DC chart in 4e is just a guideline. Want to make a check 'easy' for a character of X level, pick something you think should have the corresponding Y DC.
<snip>
the DM is free to set DCs as he likes, just as he's free to place any monster he likes. Guideline.
Well, the GM can have the 1st level PCs attacked by a 30th level dragon; have the Axe of the Dwarven Lords guarded by a single orc minion; have the gateway to Carceri by a DC 17 iron shod door; or set any other DC s/he likes. that doesn't mean that s/he is likely to get a good game.
The DC-by-level table (and the corresponding monster-defence-and-creature-level guidelines) are at the heart of designing challenges for a 4e game that will make the game work as designed (ie with reliable and engaging pacing). The first thing you want to know, as a 4e GM designing a scenario in mechanical terms, is the level of the PCs who will be engaging it.
The narration of the fiction is then expected to follow - that's what the MM, and the general characterisation of the tiers of play in the PHB and DMG are for.
Insisting that these are
mere guidelines (which I take to be a denial that they are central to GMing the game) reminds me of
this exchange on RPG.net in relation to the HeroQuest revised DC-setting chart (called "the pass/fail system"):
kallisti_dk: The Pass/Fail Cycle system, as it is called, is just a tool in the Narrator's toolbox. How you choose to apply it is completely up to you.
You could use for setting all difficulties, or never use it at all. Possibly you would do something in between, as I do.
simon_hibbs: That's an important point. The Pass/Fail is not actualy part of the HeroQuest rules as I see it. Rather it takes the place of the traditional chapter in an RPG ruleboox which gives advice on how to run the game.
smascrns: On the contrary! From my POV, of course. What I find stimulating and very innovative in the Pass/Fail cycle is that it extends the rules set in new directions. Yes, it is not a mandatory component but the same can be said about everything else in a rpg rules set, isn't it?
I wrote that I consider the P/F cycle innovative, I didn't say it is inventive, and that for a good reason: HQ2 is not the first game to come with tools to control the difficulty of the ongoing game situation based on the "narrative" flow of the game. For instance, the DD4 DMG also tries to provide tools for precisely the same purpose, and we may even say that the whole concept of dungeon crawl found in original DD was mostly a way to control the flow of the game in narrative terms. Not to mention Tunnels & Trolls.
Still, the P/F cycle is innovative in tying up all the components of the game: Setting entities, mechanical entities, game flow, narrative flow. And it does all of this in a concise and simple way (yes, DD4, I'm looking at you).
Picking up on the last of those posts, I would say that the DC-by-level chart (and the monster-level guidelines) are as "optional" in 4e as the concept of dungeon level is in classic D&D.