Further testing revealed that CorelDRAW X5 (I don't have a newer release here) and LibreOffice also "translate" vectors from Xara into bitmaps just like AD does. Inkscape, on the other hand, maintain XDP shapes as vectors. Only Affinity makes XDP crash, though.

As I can paste from XDP into other applications, I am uncertain it isn't at least a mix of faults.
Couldn't agree more. Hope someone at Xara tries to solve this anyway.