Well there may still be a chance with such a strong unit favoring system, that the defender will survive every attack, even though the strong unit doesn't die.And to be honest, it would not give a better game experience if you are in the down side of the stick A RL example: once I had the luck of seeing a warrior of mine beating the vedic aryans ( 4 barb archers, since it was a standart map ) in BtS. The odds of that happening are astronomically low, but they are far higher than the ones of the system you are advocating ( 0,0% ), and if would be a game over situation, period.
But it's easier to suspend disbelief of with spearmen always 100% loose to a tank, then to have 99% odds, but the lucky spear men happens to overcome a crucial offensive.
So Sid is not going to go back on his realization that player intuition matters more than mathematics. There will be no spearmen beating tanks in civ 5. At least not in a single turn.