The trail is between 777 only right? Still 3nm for a 380 to 380 and 8nm between 380 and anything else. With slow approach speed of the 380 a 777 needs to start a bit further out than 8 or start speed reduction earlier as it will catch up when speeds are reduced after 4nm.
Monach you said they could launch 5 777s in the time it takes to launch 2 380s. That's not correct . If mixed departures are happening you are correct the launch rate drops