nodelay,
Last time I checked (admittedly a while ago
- don't tell my LCE!!!! ), I didn't have to apply any vortex separation on departure for aircraft of similar categories. It was either two (three if from an intersection) minutes if the following a/c was lighter, or nothing at all.
The 'one minute' you refer to is just the basic route separation, which with certain a/c types can get down to 40 seconds when we use 'wheels up'. If they're all mediums and nobody hangs about you can easily get 5 departures airborne in 4 minutes.
Gonzo.