I have a question about same source WPS like 2 Burning void from 2 Seals of void (on 2 weapons), or 2 Lucky shot from 2 Jaxxon’s rings or when you use 2 Notched Bone of a Thousand Deaths.Are the proc chances stacking? If chance is 12% from 2 sources does it become 24%?Or are they separate proc chance?If they are separate does that mean that they can proc at the same time?Do they share the cd in the Notched Bone of a Thousand Deaths case?Can someone who is sure about the mecanics of this explain it? 
They technically are two separate wps, but you basically get two chances to do the same wps. And no, two wps can’t proc at the same time, even if they are the same from two different sources.
The CD with two Notched Bones will not be shared, each will go into their own separate cooldown when they proc.
You can think about WPS in the following way:
Let’s say you are an Inquisitor with Bursting Round, Chilling Rounds, and Storm Spread all at 6/10 points so each skill has a 20% chance of activating.
Now picture a line segment of length 100:
----------------------------------------------------------------------------------------------------------------------------------------
On that line segment, lets mark out the initial segment of length 20 for Bursting Round, a second segment of length 20 for Chilling Rounds, a third segment of length 20 for Storm Spread, and we’ll leave the final segment of length 40 unlabeled, so we have the following:
[—Bursting Round----][–Chilling Rounds----][----Storm Spread-----][---------------(Unlabelled)----------------]
(I’m trying to do this to scale, but please excuse small inaccuracies in proportion.)
Now, when the game “rolls” to see what (if any) WPS will activate, you can think of it as the game picking a random spot on this line segment and reading off the result. So you can see that you have a 20% chance for Bursting Round, 20% chance for Chilling Rounds, 20% chance for Storm Spread, and 40% chance of nothing at all. You can also see that the regions do not overlap, which is to say that you cannot get two different WPS activations at the same time.
Now suppose that in addition, your Inquisitor has two Jaxxon’s Lucky Bullet rings equipped, each of which provides the Lucky Shot WPS which has a 12% chance of activating. To visualize this, we take our line segment, and in the unlabelled region and inside of it label two segments of length 12 with the label “Lucky Shot.” So we now have
[–Bursting Round–][–Chilling Rounds–][—Storm Spread—][-Lucky Shot-][-Lucky Shot-][–(Unlabelled)–]
So now each time the game “rolls” you have a 20% chance for each of your original WPS effects, a 12+12=24% chance of Lucky Shot, and only a 40-24=16% chance of nothing at all.
Now suppose our Inquisitor also has two Seals of the Void equipped each of which provides a 16% chance for the Burning Void WPS. This means that when we go to visualize things in our line segment, we will need to label two segments of length 16 each with the label Burning Void.
But this is a problem, since we only have a segment of length 16 as unlabelled space. We need an additional segment of length 16 that we just don’t have!
So what does the game do? It labels everything on a line segment of length 116 and then scales that segment down to length 100.
*WPS visualized on a segment of length 116:*
[–Bursting Round–][–Chilling Rounds–][—Storm Spread—][-Lucky Shot-][-Lucky Shot-][-Burning Void–][-Burning Void–]
*Gets scaled down to this:*
[–Bursting Rnd–][–Chilling Rnds–][—Storm Sprd—][-Lky Shot-][-Lky Shot-][-Brnng Void–][-Brnng Void–]
So our segments of length 20 for Bursting Round, Chilling Rounds, and Storm Spread become segments of length 20*(100/116) which is about 17.24. Our other segments similarly get scaled down by a factor of 100/116.
What does this mean in terms of the chance of WPS? It means that whenever our total WPS chance exceeds 100%, each individual source has LESS chance of activating than its listed number. In our example, Bursting Round, for example, has a 17.24% chance of activating instead of 20%.
One important takeaway here is that if we want to maximize the chance of a particular WPS activating, it is better not to add other WPSs in a way that will make the total WPS chance exceed 100%. So if we want to maximize the chance of, say, Bursting Round in our example, then maybe instead of two Seals of the Void, we just equip one Seal of the Void, giving us a total WPS chance of exactly 100%. Another alternative to get down to (or under) 100% total WPS chance is to decrease our skill point investment in Chilling Rounds and/or Storm Spread to reduce the activation chance on those skills (or even eliminate one of the skills entirely) and spend those points elsewhere.