The only way to do what you want to do is to Make a 2 Condition Rule with Item Rarity: Unique + Item Type - SubType: Only select the item sub type that the unique is.
I explain this as well with examples here:
Note that Exsanguinous has a “Unique Only” subtype.
If you want to see a unique that has multiple uniques on the same base, you need to add a 3rd condition with level requirement to it, to only show the desired one.
That doesn’t work, stats on uniques do not refer to the regular affixes, even when they are regular sstats that are avaiallbe as affixes.
So for your Exsanguinous the rule would look like this:
Another example with the mentioned level requirement condition. There are 2 Mage Unique Helmet both using the same base type: Crest of Unity(Required Level 60) and Apex of Thoughts (Required Level 59). If you only want to see the Crest of Unity, the rule would look like this:
