@pauland, nicely put.

@All, JavaScript is essentially single-threaded. In browsers you could invoke something akin to https://github.com/keithwhor/multithread.js if your web application required it.
The XDAs are a different beast but even here there is some JavaScript being run; Smartshapes come to mind.

So where are the Xara bottlenecks: loading, Lines gallery, Exporting & Publishing? Large numbers of Pages and large numbers of Repeating Objects.
A 999-step Blend itself blended in 999 steps to another 999-step Blend takes 4 seconds on my machine. All 6 cores kick in. One works the display and the others whatever.
I can drag down my XDA fairly easily. If doesn't make me clever or Xara dumb. Overall, it strikes me that Xara needs to improve its handling of internal collection of objects, pointer and the like.
It admitted defeat when it removed the Find capability for the Design gallery.

Unless Xara steps up and addresses these concerns with quantitative detail, further discussion will get not very far.

Acorn

P.S. Just how many angels can dance on the head of a pin? If it were virtualised and running quantum, I guess at least a googol before all that information is smeared across a black hole's surface.