Geromino: Nobody here complained about BG3 being too complicated.
mathaetaes: I think the implication in that reply is if you think it's too hard, you probably don't understand all the mechanics.
You are absolutely right.
The OP felt the game hard primarily due to the complexity of this game and for not knowing what to do to win a fight without a party wipe.
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Back to the fight with that group of Gnolls:
Here are two ways to *trivialize* that fight:
1) If you are not shy of talking: Talk to the Gnoll leader, The Flind, and force her to do all the fighting on your behalf. And she will do everything as you command, including killing herself. You win the fight with no shots fired.
2) If you don't want to talk at all: Split your party and send one party member via the low-level cave entrance into the cave, disarm or otherwise pass two traps, and get close to the trapped Zhent agents. One of the agents will ask that party member for help. You agree. And a fight starts right away. Now, you have 2 Zhent agents + 1 party member inside the cave. You have 3 other party members outside the cave - right behind the rear of the group of 1 + 5 = 6 enemies. This is a 6v6 fight. Among all 6 enemies, only their leader is strong. You surely can win such an easy fight. You can *optionally* let Rugan die in fighting The Flind, saving you time/trouble later (meaning: don't be a hero, don't be on the front line, make sure she live long enough to kill Rugan).