So, with cards available on cgdb, I proxied a rogue deck and player first scenario a couple of times. Most of the skill checks I won were by the skin of my teeth, and I've lost plenty too. Looking at hard/expert token pool/scenario modifiers, I'm struggling to see how this will be beatable without a significant luck. -6 and -8? Might as well just throw in a couple of them auto-fails.

I expect to play the game on Standard difficulty most if not all of the time. I'd already decided it looked insane.

I would imagine that with future releases to improve your level zero decks the hard and expert difficulties will become more manageable (though still challenging). They weren't meant to be too easy, right?

It says in the rules that all the core set investigators start with zero experience, the implication is that future investigators may start a campaign with some experience. This, and future 0 cost cards, will make harder difficulties more manageable in the future.

I would imagine that with future releases to improve your level zero decks the hard and expert difficulties will become more manageable (though still challenging). They weren't meant to be too easy, right?

Being too easy vs being unable to advance unless random allows you? Don't get me wrong, I'm not saying it's gonna be exactly as I say, I'm just theorytizing based on my experience. Average check difficulty is somewhere within +1 and -2 of base parameters, so to secure sucessful check with consistent frequency I usually had to bump my check by 1-3 icons, and it was an introductory scenario (I'm assuming later scenarios have more challenging checks in them). Looking at hard/expert cards/token modifier distribution, it looks like if you would want to succeeed, you'd have to blow much more on your checks, and even then you'll probably fail the check. And game is on a hard clock, so if you won't get on a lucky streak, you'll lose. Or get a bad ending. This is just how it feels to me right now, it might turn out to be completely different.

Regardless, I'll be probably playing on normal most of the time, unless I'll feel like getting my teeth grinded into dust.

My plan is to play standard with starter decks the first time i am playing with people, and then with my gamegroup once we played it once we will probably play it with our own created decks, on one of the harder difficulties But still a long time till we can do that

Two words: future proofing.

With just the base game I'd expect to only be able to win using standard or easy difficulty. As the card pool grows there will be inevitable power creep. It may be slow, but it will happen - and that is when it will be useful to have the higher difficulties.

Speculation: assuming that development for this game follows same pattern as for LOTR, it is likely at this point in time they have all the cards designed for the next cycle (and likely ideas for the cycle after that). They may have looked at what was available to a player at the end of that cycle and asked "how much of a challenge would the core campaign be for a player with these cards"? They could then set up Hard to "reset" the difficulty to counter play combos. Then extrapolate for what to set the expert level at.

Based on how you get experience in this game, my guess they will target expansions towards characters who have gotten either somewhat low experience on the prior scenario or at best the average.

Thus, if you get very good experience many times in a row, you may end up feeling like upping the difficulty to give yourself a challenge. (or, you might just feel like having a more Lovecraftian experience! Ie likely death, little chance of anything else)

Completely insane is the best option
But yeah, those difficulty levels Are important when we Are more experienced and have larger card pool. I am sure that you can play even now with the hardest difficulty but that would be a pure Luck...

One other thing to remember is that it isn't strictly a win/lose option. You finish the scenario in one of multiple ways. Some may consider 'winning' to be completing with favorable outcome (XP gains, not going insane) but this is where the RGP aspect comes into play in a way that edges out the traditional LCG model. Standard feels punishing in some cases but I expect as card pool advances and various combo/meta are discovered some of that challenge of current (will be older then) scenarios will be alleviated somewhat. Within the realm of Cosmic Horror, one should probably expect to fail/die/end badly more often than beating back the bad stuff. Agree with others that it is probably future proofing to some degree as well.