- A reference guide and manual in Russian for Heroes 3.

I have a question – logically, with equal armies and equal skills (the attack of Crag Hack is equal to the defense of any hero with defense), the attack should exceed the defense level, because expert defense gives 15% while attack gives 30%. The effect of a 5% increase in attack/defense applies to the same modifiers, i.e., it affects both skills equally but in opposite directions.
In reality, it turns out that I take away a negligible number of troops from an opponent with the "Defense" skill, while my attack exceeds the opponent's defense skill by 10 points!

The Attack skill gives a 30% increase to only one of the damage components – the base damage, while the Defense skill reduces 15% from all components in total... For example, we have a hero with a high primary Attack skill (not to be confused with the secondary Attack skill, with Crag Hack being a special skill for this skill) and the base damage of a unit is, say, 50 HP. The Attack modifier will give 15 HP, and the Attack/Defense modifier can add up to 200 HP. So, a specialist in Defense (Armor) will remove 15% of the sum of all parameters = 0.15*(50+200+15)=39 HP, while a specialist in Attack receives a bonus of only 15 HP. That is, many parameters need to be taken into account to determine the effectiveness of one or another specialization.

Read section "5.7 Damage Calculation in Combat" in the reference more carefully. I agree that it is written in a complex language – it is not very clear, but the mathematics there reflects reality quite accurately. Perhaps there are some unaccounted moments, but in general, everything is correct.