You may need to level up your companions, or even level up alil yourself. I dont know what dungeon that you are facing but it tends to go better when you are equal to or higher than the bosses that your going against.
I was stuck on one for about a month when I finally beat it two weeks later I got stuck on another one.
Level 46 swashbuckler
I was once in your position when I was a swashbuckler in the gortez duengeon I was consistently dying when I got to the gortez fight and as AncientDeathbender said make sure your companions are leveled high with you because I realized I wasn't leveled high enough and neither were my companions so I did all my side quests and gained three levels and did the ones with a lot xp and gold the gold was used to buy training points for my companions. The next time I did the gortez duengeon I mopped the floor with gortez and all the other mobs This same thing happened to me with my first pirate a privateer with the old chirp place in cool ranch duengeon Find me in the game Slick Cody Jones privateer lvl 50 Merciless Ethan Jenkins swashbuckler lvl 50