For 9 attack versus 1 defense, the maximum damage per hit is 8.1 damage, and the minimum damage per hit is 4.05. A six-figure unit makes 6 attacks with attack score 9, each of which can hit or miss. I believe that attacks are rolled until one misses or the unit makes as many attacks as there are figures in the unit, though it is possible that the attack rolls are independent of one another; if the attacks are rolled sequentially until one misses, then the probability of at least one hit is P = ((attacker accuracy) - (defender defense))%, the probability of at least two hits is ((P/100%)^2)*100% (which is less than P), the probability of at least three hits is ((P/100%)^3)*100%, and so on.
Basic units tend to have something like 70 accuracy and 0 dodge, so if the attack system uses sequential until fail attack rolls, your chances of making full use of your 6-figure unit are kind of poor - using a 70 Accuracy unit against a 0 Dodge target should, if the attack rolls are sequential until failure, result in 0 successful attacks 30% of the time, 1 successful attack 21% of the time, 2 successful attacks 14.7% of the time, 3 successful attacks 10.3% of the time, 4 successful attacks 7.2% of the time, 5 successful attacks 5% of the time, and 6 successful attacks 11.8% of the time. Against a 1 defense target, the expected damage ranges are 0 damage, 4-8 damage, (4-8)x2 damage, (4-8)x3 damage, and so on for each of the given percentages.
From the sounds of it, you were simply unlucky. Only one of the figures in your unit scored a hit, and that figure only managed to deal something on the low end of its damage range.
(If the attacks are rolled independently, then for a 70 accuracy unit against a 0 dodge target you would expect that you would virtually never miss (the probability that 6 independent rolls would all fail when each has a 70% chance of succeeding is less than 0.073%), about 1% of the time only 1 of the six rolls would succeed (=> 4-8 damage for 9 attack against 1 defense), about 6% of the time 2 rolls would succeed (8-16 damage for 9 attack against 1 defense), about 18.5% of the time 3 of the rolls would succeed, about 32.4% of the time 4 of the rolls would succeed, about 30% of the time 5 of the rolls would succeed, and about 11.8% of the time all 6 rolls would succeed. I do not know for certain that the game uses successive rolls to determine how many attacks succeed. However, I do know that independent rolls would make dodge essentially pointless and I know that it certainly doesn't feel like this second damage distribution matches with how the game works.)
