I have also found this game to be crazy hard op... Its not fun when every fight is setup so the customer fails, and every enemy is stacked to the eyeballs with grenades, powers and rules they SHOULD NOT HAVE! That to me is just cheap and cheap mechanics turn me away every single time...
Its really poor so far rules wise.
Don't worry 'bout it, there is an easy mode for a reason for those who don't know the rules of the game.
Like ...there isn't, but there will be.
And for team composition i recommend Gale, Astarion, Laezel, shadowheart. You can't have all 4 of them , so depending on your class drop one of them ^^.
Astarion cause with a bow coated in poison he does insane dmg.
Laezel cause warrior op.
Shadowheart cause cleric, a little bit of healing might help if you feel you need it but most importantly an offensive cleric is quite good too. Inflict wounds op.
Gale cause mage armor lasts the whole day. You put this on him when a day starts and when a fights starts use mirror image. Then proceed to obliterate people with magic missiles lv2 or anything else. It doesn't matter, he's a mage.