As you are using AD FS, you can also reset passwords without password writeback.
AD FS has a feature that allows you to reset passwords - as long as you remember the current password. However, this feature is disabled by default, so you need to enable it using the following PowerShell commands.
# Enable update password from internal network
Enable-AdfsEndpoint -TargetAddressPath "/adfs/portal/updatepassword/"
# Enable update password from external network
Set-AdfsEndpoint -TargetAddressPath "/adfs/portal/updatepassword/" -Proxy $true
# Restart the AD FS service
Restart-Service ADFSSRV
Note that you need to restart the service on all AD FS servers in the farm.
Now your users can reset their password by browsing to https://your-adfs-server/adfs/porta/updatepassword