Also with a single die in the target range equally a hit and effects that can happen regardless of a hit

I'm afraid I don't really understand what you mean by this.

Basically, a shotgun hits on a roll of 1, so if any of the up to 9 dice you roll (3 dice, 3 rolls each) comes up a 1, you score a hit.

you end up with odd effects like spider's missing you, but still poisoning you

The enemies section of the rules for the Giant spider does state that if you get poisoned, you take a hit of damage. Was it not clearly understandable? Do you think I should re-word it?

Probably, that was unclear to me.

1. All weapons are near guaranteed hit. The lowly shotgun hits only on a 1, but as the minimum number of dice you can roll for an attack is 9 (or 12 depending on if you re-roll a total of 3 times or you have a total of 3 rolls) your odds of hitting are 1 - (5/6) ^ 9(or 12), or 81(or 89)% and it goes up from there.

2. Monsters are even worst. Giant Spiders hit 99%, web 26%, and poison 3% per attack. The P. Marine hit on 52% of attacks, Dwarves 67% and everything else is 97% or higher.

Not sure you fully understood how the combat works. The minimum number of dice is not 9. It's 3 that you start with. When you re-roll dice, you take the final results. You can't count a roll of 1 for a hit, then re-roll that same die for another hit.

A 1 is a hit, if you roll 3 dice and get no 1s, you re-roll all 3, if still no 1s, you roll a 3rd time. That means, all 9 rolls must be something other than 1 to fail to hit, the odds of which are calculated above.

The enemies are supposed to be tough. But I don't think the hit stats are as high as you seem to think they are. Spider has a 1/3 chance to hit you with a normal attack. The odds of getting 3 or 4 of a kind on 4 dice is pretty slim. The enemies only re-roll dice that are not one of the hit values.

Unless I am miss reading the rules, spiders need to roll a 1 or 2 on 4 dice with 2 re-rolls. Per the rules, in order for them to miss, they have to roll all 12 possible dice and none come up 1 or 2. The odds of that are particularly slim.

Leveling works against you. The higher your level, the more action dice you have, and the harder it is to pass luck and stamina tests. It's far safer to avoid combat and keep your level low.

Your luck is supposed to be difficult to pass if you use it too much. You also have to make sure you keep your stamina up. One way that could balance this out better though if you really think it's a bad thing, would be to subtract the total number of extra action dice you are rolling past the initial number of dice from the roll. So if you started the game with 3 action dice and have gained 2 levels, then you would have 5 action dice total. When you needed to do a "test" roll, you would subtract 2 from the results to make up for the extra dice.

Each extra die adds an average of 3.5 to the roll. At level 1, with S&R of 5, giving you 3 Action dice, Stamina 18, you would pass a stamina test 100% of the time. At level 2, now with S&R 6 you have 5 action dice, and with stamina of 18 you'd have a little over a 50% chance of passing the test.

Thank you very much for your feedback.

May I ask if you have actually played the game yet, or are these impressions from just looking over the rules?

I spent some time playing last night and either I don't get the rules or the game is just very lethal, I never made it passed 4 rooms. A single failed ambush roll cost me 75% of my health once.