Watching Heathrow aircraft approach queues, they do an amazing job, its nerve wracking just to watch, let alone what it takes to keep everyone lined up.
Some of the recat models, and matrix models use a combination of radar sep and nm for the heavies, especially with pair-wise models. One of these days, they will get ATC involved in some of the crazy scenarios they have dreamed up, ie 64x64 matrix?!?!