I'm in favor of the following difficulty curve:
Easy - Don't really need to know the mechanics, point and click on enemies being roughly enough to complete the game.
Medium - Don't need to know the mechanics to start, but need to be able to pick up on the major ones throughout the initial tutorial and first Act (how Advantage works, how to get AC to stop attacks, using roughly the appropriate Spell for a given situation)
Hard - Need to know the Mechanics even at the start. Have to have mastered the combat mechanics (maximizing Action Economy, using synergy between party members skills/spells, minimizing enemy advantages by using Stealth and positioning).
Insane - Full Mastery of the mechanics and awareness of which ones are overpowered/abusable. Always using the exact right spell at the right time. Likely requires having played through the game on a lower difficulty to know enemy positions ahead of time, what spells and abilities the enemy will use, etc.
The problem is that most people expect an average difficulty of a game to be Medium. Larian has more or less said (from what others have posted and based on their DoS 2 EA) that they set their early access difficulty to be at roughly Hard. This is to get data on which fights might be easier or harder than intended.
Given Larian's intent for Early Access, I agree with the current difficulty curve. I have pretty close to a mastery of 5e mechanics, and while I have had some trouble due to Larian's changes to the rules, I haven't encountered a fight I thought was too difficult yet. If this was supposed to be Medium difficulty? Absolutely, too hard. But it's not, it's supposed to be a roughly Hard difficulty.
