What you are describing is called Low Luck gaming. It is exactly they way you described it. You add up all the attack points and defense points then divide by 6. For every whole 6 you record a hit and roll 1 die for the remainder.
EXAMPLE:
3 infantry, 1 mech, 1 artillery, 2 tanks, 1 fighter and 1 Stuka attacks 5 infantry, 1 artillery and 1 tank.
Total attack points = 20. That is 3 hits plus roll 1 die for a 2.
Total defense points = 15. That is 2 hits plus roll 1 die for a 3.
Then after removing casualties, you do it again for combat round 2 for the remaining units. You keep doing this until one side is eliminated or attacker retreats.
This method I think makes combats a little quicker and takes out any chance of weird rolls that get you more or less than usual hits. Some people like Low Luck because you have to plan your battles more carefully and more of your strategy comes into play. There’s not so much left to chance.
Personally, I like rolling the dice because I like the chance.