In PvE, we know that putting Skill Points to "Hero Strength" will add damage to the monsters, a better weapon your hero holds would increase amount of damage done, and a better armor will reduce the damage done on your "Energy" by the monster's fight-back if there is no 1-hit kill.
Have you seen "Missed" (in turquoise color font) while the monster fights back? There is no damage on your "Energy" but you gain the experience anyway. I have observed an increase of this lately. Anyone has any idea what trigger this?