That's where you are wrong buddy. I'm not boasting how easy the game is, I'm genuinely despairing over it because the underlying combat, exploration and general feel of the fights are fantastic in this game but ruined by not feeling challenged. I'm sitting here waiting for the super autist that makes a good difficulty mod. Maybe by then even Patch 1 is out as well to fix some bugginess.
Mods will definetly come that increase difficulty, the question is what kind of difficulty you are satisfied with?
One where encounters require you to use different strategies to solve. There is no 'perfect' difficulty because at the end of the day the game has to give you a way to win but that doesn't mean I should be allowed to just use basic strategies to faceroll the content. My build choices don't really matter because almost everything works without struggle.
I'm convinced that just fine-tuning the stats a little bit more to make enemies survive initial alpha strikes and perhaps looking at the long rest supply curve can go a long way.
Nothing new. This is a conversation we've had over and over through the years. When I registered it was the same conversation about Pillars of Eternity. Before that, it was about some other game...
Fine-tuning stats, inserting time limits, limiting resources through limiting resting, these are all different approaches that come down to the same ultimate effect once combat begins.
From the position of a game designer, you want to allow more choices to players. One requirement is "have as many combinatons of class, race, stats, build, party composition, all viable". Another requirement conflicts with it - "challenging combat". The more combinations you have to provide for, the lower the difficulty bar has to be, because you are trying to account for more and more combinations.
Therefore you either have to limit playable builds, or allow all builds, but knowingly limit the viable builds - let the players discover how far they can take a bad build and if they can pass the game with it. That in itself is part of the game for some.
You mention tuning encounters but imagine you're the guy who has to tune one encounter, let's make it one from the main quest path, so that a maximum number of party compositions and builds has to be able to go through it. How much would it take you to balance it perfectly for everyone? One, two human livespans? That's why designers shower you with tools and win buttons, and then it's up to you to police yourself.
If you're drowning in "easy", or "negative difficulty", remember the maxim "The rescue of the drowning is the work of the drowning themselves".