When I equip an item that grants an additional bonus damage to a particular skill (i.e. a 2H Bow that gives +10% damage to Witch Doctor's Fire Bats), I do not see that bonus damage reflected in the character sheet DPS.
Because I cannot visually see the damage increase, it got me wondering whether or not the calculation was a straight forward increase (damage * 110%) or if there was a much more complicated formula that would result in a lower than expected actual damage output when using the skill.