I figured out why the combat results in civ can be screwy on an individual fight basis. If you follow the rough arthmetic of A/(A+D) was the attackers chance to win a round, a Regular Tank should usually bet a Regular Infantry. At an infinite number of trials, or rounds of combat, the Tank would win exactly 8 of every 13 rounds. The less number of trials, the more results can deviat from the expected results. The more trials, the closer it comes to the predicted result.
In Civ 2 and SMAC, units had 10 -40 HP. This meant that combat usually lasted a minimum of around 20 rounds. In Civ 3, units have 3 to 5 HP. This means that combat is at most 9 rounds. This means that Civ 2 has at least 2 times as many combat rounds, probably a lot more. This also means that Civ 3 has greater deviation from expected results then Civ 2.
So, in conclusion, to make combat more credible, and lower the occurence of

, you just need to increase the number of HP. I would mod that in, but I do not have the time.