Even simple things, like giving a heads up that you'll be next will help. That will allow me to spool the engines up a couple of percent, which then shaves a few more seconds (the 380 spool up is very slow from ground idle).
Yes, this is very true, especially with the A380 which looks to take at least 20 seconds to spool up/balance.
Although, I did notice a few twins that were simply not ready and rolled at around 45 seconds....I can see how trying to balance Arr and DEP on crossing runways would be a bit of a challenge, hence increased spacing.