I haven't experienced that on balanced difficulty; what party members are you using?

Some general considerations:

—Some optional fights are very challenging when first encountered, you can skip them and come back later.

—The Sword Coast is absolutely swimming in consumables. Drink those potions, read those scrolls, and shoot those magic arrows; your enemies certainly will.

—Someone should probably always be concentrating on Bless. If you aren't a cleric, I hope you like Shadowheart!

—The story wants you to rush, but don't trust it; take a long rest between large fights, even if it seems silly. You need those spell slots.

—Focus on taking small enemies out of the fight before concentrating on the large ones.

—Enemy archers (and mages that use attack roll spells) can't shoot you very well if your melee characters are threatening them.

—Bringing more than one "squishy" party member (like Gale) makes the game a lot harder. Make sure anyone who can learn Shield knows (and prepares!) it.