[Endoperez]

It's just random variation. Str 10 + spear 3 units can deal damage against a non-fatigue Colossal Fetisch with 32 body protection twice in the same turn, and then be unable to harm him for several turns while he has 30 fatigue (from Flaming Helmet). The amount of hits he takes varies a lot, but jumps in damage occur much more after the fatigue goes over 14, and then over 30 points. It's mostly 1 or 2 points of damage before critical hits, then they start dealing 4-7 points.

Because spearman can score hits even before the fetish is fatigued (no helmet, so it stays at 0 fatigue all the time), actual data and statistics would be necessary to figure out if there's something wrong with the formula. The thing that surprised me in my tests was that high protection protected you from most hits, but the hits that got through could deal 5 or 7 or 13 points of damage. I guess that's why size 2 units make so poor thugs - whatever you do with them, a single stroke of bad luck will finish them off.