It helps in some games and at some points. You can expect to lose a cav army attacking infantry in cites or metros. It is just part of the nasty RNG. I do not like to attack unless the army is at 16 or more hit points in those conditions. I will if I feel it is important to take the city right now and risk the loss. This is why tanks are best to you, if they can reach the city. It is not always an option.