I don’t know if a unique is guaranteed when killing bosses but in ~25 WT4 runs of Varshan and Grigoire I only got 4 uniques. This seem a little low to me (compared to live).
I noticed when you kill the bosses too fast they do not drop uniques.
Can someone confirm this?
No, I one shot all the bosses and always got some.
Looks like another bug.
Its most likely RNG I have killed stupid duriel thousands of times over the last two seasons and there has been a good amount of times where he does not drop a unique item. this is true with the other bosses as well.
There is a ultra small chance that you get zero unqiues from a Boss.
And only 4 from 25 runs is impossible without a bug.