This is what a combat is like, but let me give some tips regardless:
- Try using a turn based mod while sneaking.
- Try blowing up the purple barrel with a flaming arrow or a firebolt, it cooks them instantly.
- Try sneaking up to the high ground first, then shoot them as they approach.
- Try to tank with Shadowheart by casting shield of faith on her (She should have around 19 AC and be very hard to hit), while you shoot from range.
- Try disabling weighted dice in the game menu, it sometimes messes with the rolls not in your favor.