I'm also experiencing extremely slow restore times for courses, initially I thought there was a problem with my server but it turned out that FastCGI was simply timing out because the course was taking so long to restore. I ended up changing the FastCGI timeout to 30 days and courses are restoring as expected now but at an extremely slow pace. I am running Moodle 2.7.2 on Windows Server 2008 with IIS 7.5 and PHP Version 5.5.12.
I have managed to upload 3 courses at this point, the first course restore was 400KB and took approximately 25 minutes to restore. The second course was about 13MB and took approximately 3 hours to restore. The third course was about 41MB and took approximately 8 hours to restore.
This is a brand new Moodle environment/installation using version 2.6 backups provided by a learning network, I've confirmed there are no issues with the backups themselves. I'm really hoping an update or something comes out to address this issue, my environment does not require a lot of courses to be uploaded so I consider myself lucky there but I can't imagine what it will be like if I ever have to upload more than say 5 courses, at this rate that would take a week.