Regarding the hero's development, I agree with Dancing. Light and Luck are essential for a Ranger, Logistics is also highly desirable, otherwise you will have trouble in the last mission, as the Lich King will catch up with you because he moves quite far in one turn. As for the fifth skill, I personally recommend taking Education. In addition to the bonuses it provides, it also adds primary skills to the stats, starting from around level 10. At first, the effect is small, but it will improve your hero's stats and help you gain experience faster:)
PS I'll start playing this mission tonight:)