Thanks for your request. Unfortunately, I cannot provide you any reliable estimate regarding this issue at the moment. Please expect a reply before next hotfix (within 3-4 weeks). We might just fix the problem or provide you more information.
Also could you please try executing the following code and sent the output XPS to me:
Document doc = new Document("Envelope10.docx");
doc.MailMerge.Execute(new string[] { "Address" }, new object[] { "My Address" });
PrinterSettings printerSettings = new PrinterSettings();
printerSettings.PrinterName = "Microsoft XPS Document Writer";
printerSettings.PrintToFile = true;
printerSettings.PrintFileName = @"C:\Temp\out.xps";
doc.Print(printerSettings);
Best regards,
Andrey Noskov
Developer/Technical Support
Aspose Auckland Team