First of all, I know and agree with the philosophy of unique items in the game as outlined here.
However, I tend to stay away to use any uniques in the jewellery and relic slots because these are the places where you can put Obscuring (set dodge), Protective (set ele prot), and Leviathan’s (set health). These set affixes scale with the number of item slots and there are only 4 slots to put them in.
There are very few uniques that can justify giving up these slots. The only uniques I would seriously consider using are Orian’s Eye, Death Rattle (because the stats are hard to get anywhere else), and possibly the Fang ( but you can just drop it and spec it on the tree).
The uniques in other slots don’t really suffer from the same problem because they don’t compete with affixes that scale multiplicatively with the number of item slots. Yes, Enduring exists but it can be crafted on many slots and you only need 100% GB.
I’d say that the uniques in these slots should be made like Orian’s Eye where the stats are hard to get anywhere else, so there is enough justification to use the uniques instead of crafted items.