Those of you who say that if the combat system is too precise it will ruin the fun have obviously never played any RTS-s. In age of mythology for example, a hoplite will always lose to an upgraded hoplite, and in age of empires a paladin will always defeat an archer, but that doesn't make the game any less fun and doesn't unbalance it, because there is somethign called the price of a unit. An army of 20 knights costs exactly the same as an army of 20 pikemen and 20 longbowmen. Even if the knights always win the attack, they will get slaughtered on the next turn by the fresh longbows. So even if the knights will win all the fights, that will not unbalance the game because there will be less of them than of the previous attacker, which costs less (say swordsman, 30 shields, knight is 70), but it would definitely make the results of important battles more predictable (and by important battles I do not mean your 100th tank killing the spearman in the last city of a civ that is 10 times as small as you, but an early army of 5 veteran archers losing to 2 spearmen - I am sure that has hapenned to many of us before. Really screws up a good start, doesn't it?). The randomness should still be there, but only as an addition, instead of a major feature of the current combat system. Stupid results should only occur once every 5-10 fights, that will not unbalance the game and will still keep it fun for those who do not like the same results over and over again. Maybe the knights could win 4 fights with different hp left, and lost every 5th fight (not actually every 5th fight, but on average). It will also decrease the dependency of the outcome of the entire game on some random factor, because especially on higher levels the armies are so small that a player can not afford to lose 3 swordsmen to a spearman, which will not only survive, but become an elite. So in conclusion the randomness should stay, but be less evident and have a lesser impact on the course of the game.
By the way, this is a game, and most of the famous quotes used in this thread are not applicable. Surely they make you look smart, but we are discussing how to make the game more fun, not how to make it follow some principles of warfare established by some 15-th century german general (or whoever said these things originally).