Next regarding skills: Logistics is a must (to catch up to the enemy faster), Earth Magic (a slowed enemy is easy prey), Air Magic (combined with a slowed opponent - Haste increases your units' speed by 2-3 times, and that is definitely death), Tactics (successful army positioning often gives a strong advantage over the opponent ... if you use slow+haste, of course).
In the end, 3 skills remain: Offense + Defense (preferable) ... no comment.
One left: well, here it's Leadership/Luck/Pathfinding/Intelligence and that's basically all.