I'm also getting weird odds against barbarians. All of these are on Immortal difficulty. First, my scout got double strength and halved the animals' strength (Scout vs. Lion is 2.00 vs. 1.00). Second, when my shock 1 combat 4 scout attacked an orc spearman, the combat log showed two -40% bonuses along with the -80% bonus. Strength 2.20 vs. 1.42. My scout's strength was calculated correctly, but where did 1.42 come from? The unit was not damaged. Third, when my warrior attacked from a city across a river, he received the river attack penalty, an equal river attack bonus, and a "City Barbarian Defense" bonus.
I have screenshots, but it seems that I'm not alone.