1. The total skill set is overwhelming at best
The many MANY skills you can invest points into is strait up confusing.
Personally i think the skill list is somewhat limiting. You almost always choose the same skills no matter what achetype you play. If it's to difficult, why don't you play with a generated class, and increase the skills that is already choosen. I really hope Larian don't dumb it down since it's already very streamlined.
4. Combat can be very confusing and you end up not making many choices
I understand that you want players to have Loremaster before learning about their enemies weaknesses, but in reality, it would be very nice to know enemies weaknesses and immunities. I have Loremaster 2, and all I get to see is their HP and AP. It would feel more frustrating to actually know how well a spell will work before I use it. The undead machine thingie I mentioned before was apparently weak to air (I think?), and did not know until I used an air spell just to spice it up. Knowing their weaknesses is fun, but keeping them hidden will make it frustrating.
What you descibe is called metagaming. Why would you know a monsters weakness before you even encountered it. You have to experiment on your own.
Along these same lines, I have been seeing things take damage and not know why. I know walking over a terrain will cause damage (like fire and poison). But more than once I killed a zombie boar, which exploded to do fire, poison, and air damage. Or it went to an enemies turn, and a ghoul exploded in fire even though they were not on fire. This could just be me being stupid, but more than once I've had a hard time understanding everything going on.
For example, I did not know that poisoned enemies explode their fire. Maybe there was a blurb somewhere, but that is news to me.
My suggestion is that Larian make a "cheat sheet" on the tutorial that explains all the finer points.
I don't want to sound rude, but if you've played the tutorial dungeon, and still are clueless, it's really not Larians fault. In the tutorial dungeon, just after walking past the room where you get the option to estinguish the flaming floor by either attacking the water barrels or using the rainscroll found next to it, there is a tutorial about fire against poison.
