Level 34 shouldnt had much problem with the final battle. I fought my final battle at lvl35, 1 level higher, and bash them like bullying kids. I can finish the final battle by just using 1 hp potion at high difficulty. Its most likely due to your gears if you mentioned you will get destroyed so quickly. If you had a save before entering hall of echoes, just go augment your gears with better enchantments and charms. You can even try shop for legendary gears in aleroth.
Another cheap skate way is to turn down your game difficulty and fight the final battle.