Ornate Shadow Set Doesn't Stack, Why?

From completing Hunter's Calling 4 times you can receive the full Ornate Shadow set which offers good damage and hp but does not hold up to existing builds, my question is why don't they allow more than one piece to give id rewards eg: chestplate and helmet. Just seems like an odd choice

 

Cause it would be OP af

 

In addition to the above, you're supposed to only ever use one piece of the Ornate Shadow armor at a time, since you only get 1 Corrupted Soul Token per class.

 

I'm a little surprised they let you use more than one piece at a time honeatly.

 

They don't...??

 

My bad- I haven't been able to use it yet (yay finals) so I thought that the post was saying that the set should act like set items, where wearing more gave additional stats.