I've only watched a little of the streams from the weekend, but my understanding of how it'll work is:
You'll want legendary parts in order to craft Q6 gear, as normal.
You'll want to loot stuff with good star ratings, so you can eventually combine that with your Q6 crafted gear to get Q6 starred stuff.
From what I've seen it's a nice way of making both crafting and looting give you something valuable. Q6 gear is very rare in loot and, as far as I can see, crafted gear never has stars. That means you need to both craft and loot to get best possible gear.
What I am curious about, and don't know yet, is if stars are binary. If you combine two +attack speed starred items, do you end up with a bigger attack speed buff than a basic +attack speed starred item?
If the "star rating" for a stat can keep stacking, you can have potentially infinite gear improvement. If they don't stack, then once you combine enough different pieces to get a star in every category, then combine that with a Q6, you get an item that's Q6 with stars in all categories and cannot be improved further.