Extirpate is uncounterable, relevant vs Ichy and Iona Oath, undoes the same topdeck tutors, and still "counters" Gifts Ungiven. For one mana.
I was playing SS when Extirpate was printed and it simply replaced Shadow Of Doubt.
The only thing I don't get about what you're saying is how it "counters" gift's ungiven? Sure it kills gift piles relying on rcusion to inevitably get one or two cards into hand/play, but what about the piles that are just - here's four things, and two of which let me kill you?