I'm just learning Battle for Wesnoth in single-player mode, playing the first and second single-player campaigns (I won the 4-scenario brothers campaign, and am on scenario 4 of the 23-scenario Konrad campaign, on Normal difficulty), and I feel like I am either having a lot of bad luck, or there is some skewing or stickiness in the to-hit chances.
As in, I often have archers take 4 shots at 60% and they miss 3 or 4 of them. And I have lost several units when the enemy gets 3-4 hits in a row on a healthy unit.
Does "Normal" difficulty skew the to-hit odds to silently favor the AI, or am I just noticing when I have bad luck?