Round table

simplified damage formula (example):

100 Troglodytes
attack (own(4)+hero's(5)) = 9 (X)
attack skill (basic) = 10%
damage of one Troglodyte 1-3

WITHOUT ANY ATTACK OR DEFENSE modifiers we will deal 100-300 damage

now we need the difference between our attack and the defense of who we're hitting (Y), for the same Dwarves Y=7

X-Y= 9-7= 2 - this number is multiplied by 5(%) = +10% to total damage (100-300)

and we also have +10% from basic attack - resulting in +20%

100-300 + 20% = 100+20(min damage) - 300+60(max) = 120-360

P.S.: this is when our attack is higher than the target's defense (when our attack is lower - it's calculated a bit differently)
P.P.S.: in short, if the attack-defense difference is POSITIVE, then +5% to damage per each point of difference, and if NEGATIVE -2.5% of damage per each point.
P.P.P.S.: might have overcomplicated it, this is just at the thought level rather than calculations