Definitely agree that exact combat results are too vast to learn by heart. And using a calculator of any kind while playing a game that is supposed to be fast is just annoying. I think the simpler solution would be if the double circumference that lights up over an enemy unit when you can attack it would show the number of damage points caused and received inside of it (for instance a green number for damage caused and a red one for damage received) BEFORE you perform the attack.

That actually seems like a pretty good solution. An other option would be a return button with wich you can undo your last action as long as it didn't clear fog