dnd is balanced around a party of 6 , because the game have 6 stats and its impossible to cover all the rolls with only 4 party members.
You can do two to the maximum, in the character creation editor. For a warrior - Strength and Endurance (although Laezel has them already high). To the Wizard - Intellect and Charisma. So this task can be solved with the help of three characters. Oh, and there is also an artifact in the game that makes a warrior's intelligence equal to 18