Most of the adventures mentioned, including Tsojcanth, include lots of non-dungeon content, and it would seem out of character for WotC to cut that. Pure dungeon-bashing is out of fashion. So I do not believe the purpose of the staircase is to cut out walking. It's purpose must be because the included adventures could not reasonably all take place on the same plane.
On the contrary, Tales from the Yawning Portal is one of the best selling books in 5E, and that whole collection is pretty pure dungeoneering. It does seem that Tsojcanth has non-Dungeoneering material for an early 80's adaptation of a 70's tournament module, but Barrier Peak is really thin on thst front, as arr those Dungeon Magazine Adventures thst they called out.
One nice thing abour a bok chock full of dungeons...easy to take out and repurpose (though all WotC books ha e thst as a design goal, admittedly)
Anther factor we can consider when trying to predict the contents is the level range (1-13). Of the ones mentioned, only Village of Hommlet covers level 1, and level 13 is pretty high powered in 5e. I'm not familiar with all the adventures mentioned, but of those I do know, most of them fit into Tier 2.
As an estimate, one of the toughest encounters in Barrier Peaks is the Froghemoth, which is CR10 in 5e. That would be about right for a 7th level party. The Tsojcanth boss is a vampire warrior, CR 15 in 5e, about right for level 11.
Yes, thank you for bringing this up, this is an area worth thinking about.
As a comparison, here is what we have in Yawning Portal for suggested character Levels:
- The Sunless Citadel: 1[3E original was suggested for1st too]
- The Forge of Fury: 3 [also 3rd in 3E original]
- The Hidden Shrine of Tamoachan: 5 [1E original was suggested for 5-7]
- White Plume Mountain: 8 [5-10 in the original]
- Dead in Thay: 9 [6th-8th in the Next Encounters format, but the book version is probavly harder because of the lack of Encounters set-up]
- Against the Giants: 11 [8-12 for the G1-3 printing, at least]
- Tomb of Horrors: "high" [hard to judge given the 5E encoutner guidelines and lack of combat, the 1E book was billed as 10-14]
Now, for QftIS here, we have 13 Levels split across 6 Adventures, so something like:
- Slot A Low Level covering 1-3
- Slot B 4-5
- Slot C 6-7
- Slot D 8-9
- Slot E 10-11
- Slot F 12-13 rounding it out
Tsojcanth in the 1E iteration was billed as for characters Level 6-10, Barrier Peaks was billed as 8-12. So based on comparing with Yawning Portal, I would hypothetically put Tsojcanth in Slot D and Barrier Peaks in Slot E, leaving one bigger high end Adventure, a starter of some sort, a bridge from Tier 1 to 2 Sdvebtuee and one more lower end Tier 2 Adventure.
Back to the other Adventures the panel name dropped and their Levels:
- The Sunken Shadow [1-3]
- House of Cards [9-12]
- T1 Villege of [low level]
- the DL series [first one is 4-6]
- The Red Habd of Doom [6-12]
- City of the Spider Queen [10th]
- Shadows of the Last War [2nd]
- Gates of Firestorm Peak [5-8]
So, here is one possible configuration:
- The Sunken Shadow
- [Somwthing Eberron from 3.5?]
- Gates of Firestorm Peak
- Lost Caverns of Tsojcanth
- House of Cards [tying in the Deck of Many Things book?]
- Expedition to the Barrier Peaks [put higher because it really is absurdly packed with danger]