Hi,
What is the speed of only one backup ? because when i see your stats you have 900GB/H for 8 VMs, So basically , one VM is around 100GB/H.
A restauration is always more slower that a backup job. So maybe your restore isn't really slower that it.
Otherwise, do you perform a backup and a restore in the same way? Backup and restore in LAN Free for example
Regards,
Julien