I moved my gear from Monk to Huntress to check how much damage she does, and found out that Huntress auto attacks stack and deals bonus damage from Crane Stance. I haven't checked everything but it looks like it only works with elemental weapons. I got best results with penta 4x bow with water element (dps went from 46k-58k to sick 148k-170k). It worked on single earth and triple earth bows as well but not on bow with ability power. If it's problem with elemental damage it probably work on all heroes, not only Huntress.
It can be triggeres by elemental damage and can also be triggered by secondary attacks. Like on mystic with secondary attack you can trigger this shard too.
It works on all heroes, leading to that some heroes to 10-20m damage hits per primary attack.
I think i know how it works. When you use elemental weapon, damage from element is counted as secondary attack. So if you use single bow, you will get 1 stack of Crane Stance before every show (you lose all stacks when your normal damage hits enemy), if you use triple bow, you get 3 stacks and if you use penta bow, you will get 5 stacks. I don't know what about scatter shot because i haven't got any.