Mostly DSA but also Shadowrun or Traveller.
You have a situation and the PCs are let lose to solve (or ignore it). If they encounter a point where skill checks are needed then they are appropriate for the task and
The RPGs that I know best that fit this description are Classic Traveller, Runequest and Rolemaster. In standard terminology, they would be classified as process simulation, or purist-for-system simulation, games.
Traveller quite overtly has a strong world-exploration element; so do some iterations of Runequest. Rolemaster can also be played that way, but it has certain mechanical features - in particular, points in action resolution where player decisions about resource allocation and risk-vs-reward can be driven by metagame considerations rather than "I am my character" considerations - that also make it well-suited to be drifted towards story-oriented play.
not scaled for levels (4E) or story significance
That you draw this contrast is interesting; in 4e, "level"
is a measure of "story significance". That is, for 1st level PCs, 30th level challenges do not have any immediate story significance. They may be there in the background, waiting, but they will not be encountered by 1st level PCs. Conversely, for 30th level PCs 1st level challenges have no story significance. If they figure at all in the fiction, they are not points for the application of the action resolution mechanics, but simply to be narrated through.
What 4e does, by combining level scaling with a pre-published package of story elements (very roughly, kobolds at the bottom, drow in the middle, and demon princes at the top), is ensure that a generice 1st-to-30th campaign will be one in which the heroes experience "the story" of D&D. To that extent it's not about world exploration or storyline exploration, because the basics of the world and of the storyline are predetermined. (Somewhat similar to HeroWars/Quest, in which the Gloranthan Hero Wars provide a pregiven backdrop to the events of play.)
The Dark Sun campaign materials provide an interseting published example of how the basic mechanical framework, including scaling, can be adapted to support a game that unfolds against a different story backdrop. Chris Perkins Iomandra campaign (that he discusses in his column on the WotC site) shows another, unpublished, example. And I'm sure 4e GMs all over the world make changes - minor or major - to make the story backdrop fit their and their groups' particular conceptions of what the story backdrop of D&D should be.
But whatever the backdrop, the basic 4e framework means that it will have a direction and an escalation - start out small and local, grow to be big and cosmological (whether that's demon princes or dragon tyrants) - which distinguishes 4e from a process sim, world exploration game.
4E made it quite clear that combat is the core of the game and that if you didn't want combat you should gtfo.
Combat is the preeminent mode of confict resolution in 4e, yes.
It would not be impossible to run a combat-free game of 4e, resolved using just the skill mechanics, but I would wonder why you'd bother. Your PC sheets and monster descriptions would be carrying a lot of unnecessary payload. That said, I doubt that I am the only GM to have run
combat free sessions of 4e. It's non-combat conflict resolution mechanics are pretty robust.
Yes there were skill challenges, but they were broken, as was the skill system in general and lead to mindless dice rolling depending on what skills the DM uses for the challenge.
I don't think this is true. I refer you to the threads I linked to above, as well as
this thread.
I think it's implicit that what the PCs are facing is assumed to be dramatically appropriate for their level.
Yes.
4e DMG pg 42 is clear that the idea is that the DCs scale with character level. It says "A quick rule-of-thumb is to start with a DC of 10 (easy), 15 (medium), or 20 (hard) and add one-half the character's level."
Yes, but I think it is taken for granted that the narration of the fiction of the challenge will be appropriate.
For intance, on page 64 of the 4e DMG is the following text and table:
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. Some of the examples below show DCs for breaking down doors or opening locks, and also show the level at which a character should be able to break down the door with a Strength check of moderate difficulty. Thus, that level is a good rule of thumb for dungeon design. Don’t put an iron door in a dungeon designed for 10th-level characters unless you intend it to be difficult for them to break through. . .
DCs to Break Down Doors
Code:
Strength Check to DC Level
Break down wooden door 16 3
Break down barred door 20 9
Break down stone or iron door 25 18
Break down adamantine door 29 29
Break through force portal 38 —
"The world changes with the PCs' level" can be addressed by providing tables of what common challenges (e.g. locks, doors, walls, etc.) of varying DCs represent in the real world or asking DMs who are concerned about world-building and simulation to reverse-engineer the real world situation from the calculated DC and to maintain consistency while doing so.
If you're willing to set the DC first and reverse-engineer what's happening in the fiction (i.e. instead of asking, "This vault is protected by a iron door. What's the break DC?" you ask "The break DC of the vault door is 25. What sort of door is it?") then a table like the following could help
Much like the table on p 64 of the 4e DMG!
when running 4e published adventures you need to treat the 'delve format' fights as only one possible outcome, no matter how many pages are dedicated to them.
<snip>
It's a shame the terrible Delve Format gives the impression YOU MUST FIGHT 30 ENCOUNTERS TO COMPLETE MODULE - it's terrible design, and completely unnecessary. The typical 4e adventure works best IME if the PCs avoid or non-violently resolve 1/3-1/2 of the encounters. Ignoring any 'attacks immediately' text about half the time
Yes. This is also the only way to treat skill challenges as presented by WotC - they are "GM's advice" on how to interpret and resolve likley player choices for their PCs. (And if you look at how Robin Laws' Narrator's Book for the original Hero Wars treats the extended challenges for its example scenarios, you can see how little change in terminology and presentation is required to make this crystal clear.)
Thunderspire Labyrinth alsop has some potential.
I have some advice on how to adjust this to improve its play
here