Software Installation Very Slow without Internet Access

I have been using Windows 8 Client Hyper-V for a while now and must say it works like a treat - except for one thing: it is practically impossible to give VMs at the same time NATted internet access and connect them to other VMs and to the host. Windows Internet Connection Sharing (ICS) just does not work reliably and I have found no other product to use instead.
Windows General