Waiting time can be shrinked a lot and we could even do other stuff while waiting but that requires people more focused i cannot ask for 30 minutes for a cannon user and it comes last minute or I've even to take over.
If we wanted we could do a champion run till -5 to tequatl spawn so people don't get bored ... but that requires all turrets all groups all defenses are done in that time without commander pledging people to do it.
Same goes for triple trouble we could start organization when the -5 minutes timer starts (i've seen it done so let's not argue it's impossible) so we can jump to map just 10 minutes before event start organize split up and dry run during escort (with 5 people doing escort).
The question is people would be up for this? if we wait too much and cannot get it organized we'll get just fail, if we can get it organized with a strict time window everyone will save time
On DS and TD i don't really see any way to save time aside as you say some people going afk for a bit. The event start immediately and you've to do them all, you cannot jump for a meta or whatever. Maybe we can save a bit of time on TD by starting 30 mins later (?) and rush through pre events (you cannot skip them or you won't have a decent meta) but then we won't get 200% participation on the first part.
I don't really remember which event we are doing i just remember when we are doing them i let nova remind me
For the evening/mid day stuff. Personally I've lunch in the middle as well and i usually use the time window before or after one event to do it. splitting between monday evening also allows a better distribution for people who cannot do it on evening.
Aside that personally I'm busy with wvw stuff on tuesday thursday sunday evening and saturday evening is currently wvw reset so anyone really enjoying wvw won't be there on a saturday evening.