We managed the first mission with four characters (Brute, Spellweaver, Cragheart, Scoundrel) , but it was close. Due to positioning and such we avoided damage from some of the guards in the first room. We also made good use of the traps in the second room. The Cragheart has a good card that gives many enemies Disadvantage that was useful, IIRC. I think a key point is to not use the loss effects on the cards before late in the scenario.