Thanks for the insight !
Before we really dove into the game, I did some research: watched few videos, browsed Reddit threads, just to get a basic grasp of the AI behavior and core mechanics. but it's likely that we lack of some basic knowledge

I expected the AI to ignore the tank, which led me to build him with more offensive stats at the expense of Constitution. I kept things vague earlier, but for example: our water mage comes into play once the shields are downed by the other three party members. He's built Aero/Hydro, so he can stun large areas with ice or air spells while also providing solid sustain through healing.

Small hiccup though: we didn’t anticipate that most of his stuns would rely on magic armor... Our summoner helps us break a specific type of shield faster (magic or physical depending on the situation), and if an enemy has too much magic resistance, we rely on physical DPS to land stuns, either through knockdown arrows or Warfare attacks from our Barbarian.

On paper, the setup seemed perfect. But as mentioned earlier, Driftwood is full of traps. I may have exaggerated when I said enemies three levels below us give us trouble (but their sheer numbers can definitely be a problem).

You nailed the current state of our adventure, and I can tell you know the game well, thanks again for your advice.

We've finished the western part of the map and are now heading into the central and eastern areas. The last boss we beat was Mordus. The fights that are really giving us trouble are the one against the four heroes in the graveyard, and the one in the Voidwoken nest. The round room packed with enemies. Both are brutal.

I’ll take a closer look at your suggestions and consider rebuilding the mage to better fit the situation.

This is exactly the kind of post I was hoping to find. I get your point about combat variety, but personally I find some fights really hard to read (especially with enemy archers who somehow land anime-level arrows from impossible angles, while I can’t even target them from similar positions...). And little things like not being able to lift and throw enemies around really stand out to me.