On a p2p link, for your traffic vis-a-vis itself, there's no point to MetroE QoS. Whatever QoS you might need, would/should be done on your devices that connect to the MetroE circuit.
However, where MetroE QoS might be of (great) importance, even on a p2p link, would be how your traffic is treated across the MetroE network relative to other customer's traffic. Unable to say what will happen to your VoIP traffic if you exceed your CIR for it. If your MetroE provider doesn't prioritize it, relative to other customer non-VoIP traffic, then using their CoS markings is unnecessary. If they do prioritize, relative to other customer non-VoIP traffic, but don't really enforce a CIR for it, you could consider marking all your traffic with their VoIP CoS tag (to insure all your traffic gets the best service across the MetroE network). If you provider does enforce a VoIP CIR, then depending how they enforce it will matter to how you use it.
