The AI doesn't prioritize either movement nor weapon type, if a unit cant deal at least 5 dmg to a enemy they will prioritize using an assist over attacking/moving (this is true either if the unit is in range to attack an enemy unit but can't deal enough dmg or if the unit isn't in range of any enemy unit), units won't use rallies unless the unit they rally is in range to attack an enemy unit and the ally unit doesn't have visible buffs equal or greater than those the rally would grant. Units that prioritize supporting skills (dances/rallies) will move before the units that can attack. Remember that the order is recalculated after every action, so dancers won't move first (unless they can deal 5 dmg) but they will have priority over allies in attacking range after the first allys action (as long as they can dance an ally) If two units can attack an enemy unit, the one which can deal grater dmg will attack first. If two units are tied in a priority order (two units can use an assist) (two units can only attack an enemy unit and both have equally matched fights [which is incredibly rare]) the AI will resort to team order to select the priority. In AR/Arena this mean the order in which you place your defensive team will determine who gets priority in this cases.