I have a vector diagram (saved as PSD) that seems to kill my CPU whenever I try importing it as a prop ... which I didn't really expect to have happen on a brand new PC with a hex-core i9. The prop is reasonably complex (it's a rubbish pile containing a variety of objects) but not overly so. Other simpler objects are fine.

Is there a limitation on what CTA3 can import as props, and is this heavy taxing of the CPU something normal that occurs when importing objects?

Cheers
Andrew M. 

As I know, you can adjust preference settings to control import vector quality.
That will improve your CPU loading.