I've encountered an issue which seems to be present on affinity designer and publisher. Is it user error or a bug?
I made a business card using publisher which was all fine, I used the preset styles (cog shaped icons) and just changed the colour. I found when it came to exporting I did the usual CMYK pdf, 300dpi and the text came out very blurry and pixelated. I tried again as an eps and jpeg, then opened in adobe illustrator just to see, the same result. I then had a thought to export as a 600dpi file and the quality improved but not enough and finally exporting as a 1200 dpi pdf did the trick with the quality I was expecting for printing.
In my experience, I've never had to export more than 300dpi, I've worked in a small print shop since 2014 and we print half our jobs in-house and the other half are trade supplied
I'm attaching screenshots.