Effectively, both of you have an interest in having some content not be bypassable or trivialized such that one idea makes the whole problem simple to solve (thus cutting 4 hours of content to 1 hour?).
Yup. In our group individual sessions last a long time. We meet on average only once a month, but when we meet it's 10 - 12 hours of gameplay! If I'd let them get away bypassing a whole session's content, there wouldn't be a lot left to do, except a few 'random' encounters and preparing for the next major event in the campaign.
So, don't say "there's no shortcut" if you think that'll kill all the fun stuff you had planned. Don't say the orcs and hobs won't go to war against each other or sign a truce if the PCs try.
That isn't what I meant: I would let it work, but only for a while. E.g. they'd bypass several smaller scale encounters in exchange for a single larger scale encounter. They'll still save time, probably have an easier time, all things considered, and are likely to gain a greater reward.
If you think they might try to broker a full peace or redirect both sides against each other and watch, make some notes about the outcome of such a possibility. maybe the 2 tribes unify too well and actually go on a bigger campaign of war.
Two things:
First, I don't like to prepare too much for outcomes I consider too unlikely (as mentioned, knowing my players, they're much more likely to not ally with anyone).
The whole point of leaving key things open when preparing is to be able to adjust the adventure during play to deal with the unexpected (see below).
Second: The presented scenario isn't fleshed out. It's a hypothetical scenario I presented to illustrate my point. In a real scenario there'd be an important goal to be achieved by entering the dungeon or a crucial mcguffin to be gained and I'd have a better idea about the situation as a whole.
In a campaign, every action of the pcs will have consequences. So, yes, if they managed to achieve a lasting truce between the two factions it would likely change the balance of power in the area. Likewise, if the factions destroy themselves, they'll leave a power void that is likely to be filled by a third faction.
But that is outside the scope of this isolated scenario.
What I consider one of the big advantages of my approach is that I'm usually able to control very well, how far we'll get in a session. Here's where the aspect comes in that The Shaman would hate so much if he could conjure such a strong feeling over something like gaming
Say, the above scenario was about finding a McGuffin that is hidden somewhere in the dungeon. What I might do is the following:
When preparing for the session I'd decide on a couple of likely places where it might be found:
- the hob-goblin's treasure chamber
- the orcs' treasure chamber
- a secret chamber unknown to either faction
Now depending on what my players do, I'll decide during play where it actually is. E.g. if they ally with the hob-goblins, I might decide, it's in the orcs' treasure chamber, and vice-versa.
If I should find that I have misjudged and they have a too easy time, I might do it the other way around. If they find the secret chamber too early, instead of the McGuffin they might find a potent magic item instead. Alternatively, they actually do find it, but are then hunted by one or both factions.
So, these decisions are influenced by
- the pcs' actions
- the challenges so far
- the time left to play
Ideally, using this approach I end up having sessions that always have a good mix of challenges, combat and otherwise, and come to a satisfying conclusion (or less often end in a cliffhanger).
So maybe this is my invisible railroad: Trying to reach a railway station after each session?!
In over seven years, this has worked in all but one or two sessions, which is considerably better than with any other DMing approach I've tried.
It may not be for everyone, but it's ideal for groups in a similar situation as ours.