On areas were you don't see an enemy on sight, lead with the character with the highest perception to increase your chances of detecting traps.
When you see enemies, take the time to prepare. This is the biggest thing in my opinion that noobs will get wrong. Split your party, apply your buffs, position and then engage. Someone already mentioned mage armour. Some buffs last until you rest, so use those as soon as you return from camp. You can even use turn based mode to apply buffs that don't last as long, like poisons on your rogue before that backstab. Maybe your first attack might me gale launching a few enemies from a roof, or astarion backstab one shotting a mage that would potentially put one of your guys to sleep.
Party composition also plays a big role, so does gear and stats.
Use crowd control if you don't think you can do enough damage to the enemies (sleep, knockdowns, whatever).
The goblin camp thing that you mentioned is a bummer. I had the camp just turn on me in an instant as well. I do not think that is working as intended. Still depending on how you approach it, you can clear the whole camp.
This is my third playthrough with a light domain cleric, laezel, gale and astarion, and I'm just rolling everything tbh, no problems.
I had the same problems, especially with DOS 2. But after getting my ass handed to me, my second playthrough was a lot more solid, even in tactician mode, due to better character builds, team comp, and pre fight preparation.
