I really hope they change it to 11pm-5AM. 8pm is the time when people are actually playing it for the most part.
If I remember it correctly, they're based out of Australia. That should put the daily reset at 10AM their time. It's an appropriate time in case anything goes wrong.
Most of the devs are australian based, server is based in Texas or something. Believe J-wiz is the one around those parts.
As a suggestion to the Devs, could there be a Campaign Reset Timer that shows on the map, like there is for the MP chest? That way we know when the dungeons open back up.
A very popular request during beta for stores and adventures. Not sure why it's not in though. Either harder than we thought - or deemed not to critical to make it into the game yet.