I understand your concerns about the identification of the West_Asia autosomal component with the Indo-Europeans. I find it interesting, and something to consider, but I also regard autosomal dna as very tricky, since it is subject to recombination and the laws of dominance and recession. But I am far from an expert on the subject and so am dependent, at least to some extent, on what others with more expertise have to say.
I am also not an expert on Sardinian history and prehistory, but from what little I have read on the subject, it would seem to me the biggest IE impact on Sardinia came from the Romans, and that would have been an impact much removed from whomever the original purveyors of Indo-European were. The fact that Sardinians currently speak IE languages doesn't necessarily mean that those who brought IE to Sardinia altered the genetic make-up of the island that much.
I know that Sardinia is fairly unique in having the highest frequency of y-haplogroup I-M26 anywhere in the world (I think it's around 40%). I-M26 is also found among the Basques, and some scholars have claimed to see a connection between what is known of ancient Nuragic (the early, non-IE language of Sardinia) and Euskara.
Coon thought Sardinia was settled during the Neolithic and that subsequent population movements had little effect on its people.http://www.theapricity.com/snpa/chapter-XI16.htm
The following is from Chapter XI, Section 16, of his book, The Races of Europe
Sardinia and Corsica were peopled at the beginning of the Neolithic by a race of short-statured, dolichocephalic, low-vaulted, brunet Mediterraneans, coming probably from several quarters, including the adjacent European coasts, North Africa, and the eastern Mediterranean. Subsequent immigrations of other Mediterranean peoples have affected the racial composition of these islands but little.
Just the same, Sardinia has a fair amount of y-haplogroup R-U152, especially in the northern part of the island, and one would think that would reflect some Indo-European genetic impact, probably mostly Italic.http://u152.org/