You need to pick cards which help your weakness also. So if you have a char with low wisdom etc pick some allies or items which help this. I completed the first scenario with Ezren and I would say it was pretty easy. Thieves tools a mace, attack spells invis, night watchman troubadour.
Also I completed it with my gf as valeros she was kyra and died. She forgot she could heal lol. But in fairness closed 2 locations and died heroically chasinv the villian (he escaped to where I could finish him)
Our first game of 3 valeros merisel and seoni we lost due to time. Seoni died this game being reckless (my gf again).
Picking good cards and also moving if you know there is something terrible in the area you are in are important.