we just got released the version 8.4.4 and can confirm that the problem is solved with this version. Edge opens web pages fast, Outlook attachments are opend fast, too.

any news to delivery date of Secure Endpoint Connector 8.4.4.?

Having the same problem with Edge, we discoverd Cisco Secure Endpoint to slow down openig files from Outlook 365 and Adobe Acrobat as well.