it's a skill that does work as it says in the description. the ac of the person u're attacking at that time will be xx% less (depending on what llv the skill is at) for your hits/dmg
yeah but when you compare AC drop's increase damage and the increase damage from multi/xfire, it's not worth using it. Warrior's piercing on the other hand can pierce spells like ds which is 90% protection and is very noticeable.
it's only for those 3 (i think it's 3 at least) hits u get when u load the skill and btw, the skill doesnt work when u're using a pretection spell/skill