After playing Zombicide BP in the summer, and playing Conan some weeks ago, both of which are balanced in a way that both parties have roughly equal chances to wipe the other one from the table, i was just keeping thinking about it. Zombicide is designed to be the fast arcade game for an evening "inbetween".
In Zombicide, it's the board game that can wipe you out, and if you do well and find the right stuff at the right time, you can clean out the board quite neatly as well.
Conan as well is a game that is roughly balanced; at least it is marked "easy", "medium" and "difficult" - whereas i might at least imagine how you could do a progression system there.
So here we have "balanced" games, but clearly they do something in those games that is not the intention of Heroquest. The progression system wouldn't work if both sides have equal strength.
Me, i am on the role play gamer side.
So what about balancing now? What's that for Heroquest?
I would say, a game like Conan or Zombicide is too hard for Heroquest. If you lose half your heroes each time, it breaks a lot, including motivation.
Same happens if you play the maze all over again and again - that's just boring.
The point is: "i would say". It's absolutely personal.
Of course you may have a different opinion. If you meet only once in half a year, an equipment progression system might just be the wrong way to go. If no-one remembers his heroe, you don't build up a narrative, and without the narrative, any progression is quite pointless. Then, for you, balancing like in Conan might just be the right way to go.
So in the end, balancing is about getting the difficulty under your personal control. And that's a form of art.
I don't want two things to happen:
* I don't want to have the result of the game narrowed down to the point that everyone can see in the beginning how it ends. I remember playing the settlers boardgame so often that in the end i could say from a glance on the starting positions who would likely win. I stopped playing the game because of that.
* At the same time i don't want it to be too randomly, because then i effectively lose the control.
* I don't want to mis-estimate to a point that I crash my hero group into a wall, or giving them a walk in the park.
To make it not too easy, my personal goal is to have base game compatibility. I want to be able to reuse the most basic models even in the late game. That's a hard one: I never played kellar's keep and i just had a short glance on the ogre hordes before i died, but i can't fight the impression that the game itself is not necessarily always base game compatible.
I did my four color questbook only to allow the heroes to progress as they like and it would still stay interesting.
There shall always be the threat, sometimes there should be someone dying so that they never feel safe; but then... that's it - well, that's it, for me.
The real point is:
Once you have the difficulty under control, you can do with it what you want.
You can harden the game to the point that only one or two heroes survive, if that's what your group likes.
You can soften it down to a point that leaves a small threat, but the real attention goes to the carefully planned special event in the quest. My opinion, those special events are what keeps a player group addicted.
Or you go the medium way if you don't have too many equipment items in your variant, so that someone dies regularly and has to re-buy from the beginning... just care that it is not always the wizard please.
So that's balancing:
Control the difficulty to your liking, without having accidents in the one or the other direction.
I think that Mohawk's Questimator does a solid job in estimating the basic and medium elaborate monsters. It gives you the result with a variance that leaves sufficient room for speculation if you win or lose: The variance is typically 50% of the complete result. So if you plan a quest that cost 15 life points of your group, you don't know if it will be 7 or 23 life points in reality... and 23 is quite a killer quest.
It is then the proper task of the quest planner to estimate all the magic and special events and special traps that he puts into the dungeon, and calculate it on top of the Questimator value or discount it from there.