The game starts out hard and then gets easier as you get more tools, but there’s a low-level build that helps you even the odds until your other characters catch up…
Bring Karlach and have her throw things. She gets two attacks a turn at level 3 with the Berserker subclass and Enraged Throw (most other classes have to wait until at least level 5 for a second attack), an enormous boost to her damage and accuracy from Tavern Brawler at level 4, and then a third attack at level 5. Potions of Haste or Elixirs of Bloodlust give her even more attacks, and certain magic items boost throw damage significantly. You can buy a reusable throwing spear for her in the goblin camp, but even before that you will have lots of javelins, axes, and daggers to throw. You just need to pick them all back up after the fight.
(Some people say that throw barbarians make the game boring, but Karlach can pick up and throw small characters like goblins. This never gets old. Imagine that Karlach is about to win the NBA championship for you with a three-pointer, the basketball is a goblin, and the basket is another goblin.)