What I mean by this somewhat confusing topic sentence is that:

If you play a Demon Hunter 6M, any spender you use will affect and get its damage multiplied by that skill % damage bonus and as well, Sentry % damage also multiples through.

If you play a Crusader, Holy --> Heaven's Fury is used, Darklight Fist of Heaven's both can have % damage added without much interference.

If you play Barbarian when they Leap Quake - They get the Bonus to Earthquake on all of the Earthquakes the set enables them to use.

If you play a Witch Doctor on either Jade ( Haunt + Searing Locust directly multiplying the damage on proc) or Pet like Zuni (Muliplier for Garg, Fetish Army, and Zombie Dogs)

*********If you play a monk---... Dashing Strike % damage bonus has no affect on the damage done by your Dashing Strike proc of 1000 Rainments **************

********** If you play a monk--- and you use Sunwuko, then you will receive no additional bonuses from any skills % damage when Sunwuko's procs *************