I wanted to like this game, I really, really did, but I hate the campaign structure. I'm wondering if there are any 3rd party missions that are similar in scale to the original Descent. Large, individiual missions that can be played over a few hours and when it's done, it's done.

Maybe try just playing the finales?

Give the heroes and Imperial a bunch of xp, creadits and influence.

Buy a bunch of stuff and have a go at just the finale.

I'd say you can figure out how much xp winning each mission before the finale would be gained by the winner, split that in half. That's how much xp each hero and the imperial gets.

Give Imperial 1 influence for each mission, and give heroes 400 credits per mission, and say +50 per mission assuming 1 crate gotten per mission.

To answer your other question, I'm not aware of any third party missions, but there may well be some out there.

I was about to suggest the same - play story missions standalone.

For full-length campaign finales something like 12 XP and 6000-6400cr for 4 heroes, 12 XP and "some influence" to purchase 4 agenda cards from a draw of 6-8 for the imperial player.

Play skirmish. It is excellent, and is flexible to house rules for complexity or length of game. I haven't gotten next to the campaign at all.

Play skirmish. It is excellent, and is flexible to house rules for complexity or length of game. I haven't gotten next to the campaign at all.

It's been a while since I've looked at the instructions, but isn't the skirmish only 1v1?

Hoth introduced a four players variant. Also it would be easier to create a mission for Skirmish on a bigger map. I think using training ground as a Base would make a good 3 player variant

The considerably shorter Twin Shadows / Bespin campaigns might be more your style.

If you want to just play single missions however you'd like for one-shot sessions, I'd suggest checking out this PDF on BoardGameGeek: https://boardgamegeek.com/filepage/132078/singles-missions-if-mid-campaign It tells you how to assign XP and Credits for any one-shot mission. All the players upgrade whatever they want using whatever that chart says, then you play the mission. Easy as pie.

Play skirmish -