Indeed, whenever one deals with large numbers it will be safe to assume a Gaussian distribution. The trick is to find where the mean and standard deviation lie (in our case, at Hard and 1 spot away, respectively). I voted for Hard, because it is a natural compromise.
Most people do not want to be led by the hand, nor will they be hard-core enough as to take into account all the possible ramifications of every little action (these grow exponentially!). Ultimately, things such as these break immersion from the game experience, since plot difficulty is generated via NPC interactions and/or performing actions in the game environment which activate certain triggers. It is the motivation behind these that ultimately makes or breaks the "realism" of a fantasy experience.
Should you be required to be careful when dealing with entities malevolent towards you? Yes. Should you constantly be on your guard? No.
Should you have some insight into the ultimate consequences of your actions? Yes. Should you have information that allows for a trivial approach (i.e. information you are not supposed to have)? No.
Should you be required to do something complex to live a life (even an adventurer's one)? No. Should you be required to do that for additional perks, for something "extraordinary"? Yes.
This is by simple analogy with the so-called "everyday realism".
Having said that, saving often (and without overwriting) is a common standard among RPG players and while it assuages many of the problems with the difficulty of the plot, it also breaks immersion easily. The trick is ultimately to have people return to previous saves more often in order to explore possible plot options, than in order to bypass dead ends. (Which might require an improved save management system - more plot-centric, maybe as if reading a choose-your-own-story book, but perhaps search & sort are equally needed). Then again, if the dead-ends are FUN (as some of them were in old-school RPGs) then people might explore those as well.
Needless to say that, ultimately, the game is a program and its execution flow complexity increases with the number of things it does. This leads to the paradoxical conclusion that the main story should be simple so its flow can be easily monitored/prepared for beforehand, while the optional things may be more complex as they are not required by definition. One would expect that the main story would be more complex, while the side-quests/activities to be an afterthought.
And here is were good storytelling is required. How do you present something that is conceptually simple and provide for embellishments that are not necessary, that do not affect this simple flow, yet somehow feel as an organic continuation such that the whole will always be more than the sum of its parts?
Finally, it is all about immersion. The player should feel that he is not simply playing another game, but something special. In reality, a game will always be a game (i.e. an activity with some rules performed for entertainment purposes), but it is the presentation, the "how" and the "why", the link that it forms with its players that allows it to transcend its condition and become something more...
I have all the confidence in the collective at Obsidian Entertainment that they are capable of such a game. Not least of all because of the previous experience, but also because Project Eternity aims from the start to recapture this feeling of something special from a tried & tested category of such games: the isometric, party-based RPGs.