i think its gonna be something like this:

Before doing content you have a "Number" which presents your "luck" (at rewards) that number is neutral at first.

You go to you first content with your neutral "luck" and finish it.

Now you have two options, either do the content again and the "number" turns slightly negativ.
Or you do another content which ups your "number" and changes your "luck" slightly positiv.

Depending on whether you do different content everytime in which case your "luck" stacks positiv, or you do the same one again where your "luck" stacks negativ.

OR

Depending on your loot luck it changes personal drop rates.

Say you get drop first run, your drop chances on that specific content get lower.
On the other hand getting no drop, increases your drop rate.

Either way, beta is almost around.