You got a point there, some tactical features like attacking and defending with battle formations would bring a bit of strategic & fun element to the game rather than just mathematics.
By formations I mean that attackers would be able to set attacking formations and defenders defending formations. And these formations would bring about boost and reduction to their respective armies when the battle happens.
For example, the attacker choose a formation called cavalry charge and defenders had kept his city defending units at phalanx formation. Then the battle would give a boost to defending team and a reduction to attacking team.
This topic was raised before, I hope they are still in development