This has often puzzled me about the Tarim mummies too. They are often portrayed as rather north European (this is to some degree disputed) but yet most of their mtDNA was asian.
When I first saw photos of them I must admit I thought "Blimey. Dead Russians. There's a turn-up for the books."
('Russians' as in, citizens of the former CCCP, that is: disclosure; FTDNA has me down as '100% Orcadian'. I detest the place (small islands creep me out) and have absolutely no family connection. I suppose they mean "NorthWest European"? Just to show the subjective filter I'm looking at the Tarim people through).
Just shows how tricky and misleading the (non-)linkages between genetics, phenotype, culture and languages are, and I prefer to run away screaming incoherently whenever such factors are foisted on the archaeology as a done deal. Keep them in their own clearly defined boxes, and they'll be fine, and wonderfully useful, but any perceived intersections are going to have to be
very harshly scrutinised.
The current data coverage and quality is going to have to improve a heck of a lot before I'll touch any of that stuff with a bargepole, outside of wild blue-sky speculation for its own sake. Usually after exceeding the government's recommended daily number of units.
These studies are cool; Oetzi, permafrosted graves, mummies, and if I was dictator of the world they'd be mandatory for all diggers who have to deal with these very rare discoveries.
Some hint as to the related material culture(s), dating material, DNA, and a desiccated, distorted and probably weirdly discoloured representative of the group's appearance, all in one neat gift-wrapped box? Bargain!
If only they'd been buried "with letters in their pockets" as either Mair or Mallory said ages ago.