Reading through Helvetesfortet it definitely has a lot of problems.
It's too bad because one of players would be all over a "good vs evil fight the evil overlord" quest game.
I'm not even super opposed to a fairly linear overall quest, provided the players have some freedom doing the specifics, but it gets a bit rough, doesn't it?
The opening setup has potential: Demobilized mercenaries looking for trouble and some extra coin is a good setup, but the hook is pretty weak.
One of the "hooks" is that a guy in the company whom nobody really knows walks outside the inn.
If anyone talks to him, he says he doesn't really know anything and if they leave him alone, he disappears.
That's supposed to be enough cause to go ransack his room for evidence. It's pretty forced.
The opening would work better if the players were flat out hired to go infiltrate Nidland and get the information needed and I'm not sure why they didn't go with that option. It's not like the adventure is afraid of railroading you later.
You go to the dwarf city, which is fully detailed even though you basically just get told to piss off.
Even if the players sneak in (or just massacre every dwarf they meet) the adventure flat out tells you that the players can't open the gate here, even with magic).
So this section could be half a page long.
The players get funneled through the orc mines (which is fine, its Moria basically), they end up in the grave. Here, they HAVE to check out one of the side graves instead of just heading straight through it.
When they do, they HAVE to fight the obviously super dangerous undead guy with obvious magical weapons (instead of running away).
Then they have to pick up the evil screaming face demon-artifact (instead of ditching it immediately, because it's obviously evil, something the adventure even says certain characters can tell at a glance).
Then the group gets captured when they reach the surface.
Then you have to explain why they don't just call on their magical pegasus friend to come save them in an obvious time of need.
Then you have to explain why the soldier minions of the evil sorcerer lord don't confiscate the obviously evil demon artifact they are carrying.
Then they get hauled before the sorcerer overlord for him to twirl his moustache and now they have to use the demon artifact which blows up the castle and they get whisked away on pegasus-express.
(also am I not understanding something right? The "Bestraffer" ends up just heading to Vicotnik to help him anyways after being freed so since we know the demon can communicate with people, why didn't it just try to get handed over to the him to begin with, The One Ring style?)
It's all pretty rough. You can get away with a couple of "isn't that awfully convenient" moments in a campaign and the players will forgive you as long as they are having a good time, but when it starts compounding on itself like that, it starts eroding the players trust.
It's too bad, like i said, one of my players would love this sort of thing if it was a bit more gracefully handled. I'm not sure if it's worth trying to fix it up or just take some of the ideas and use them elsewhere.