As an attacker you can adjust your night time. These 3:30am-8:00am battles are just acts of cowardice.
I honestly don't know what's worse. A 9 AM battle means the majority of NA has to work, and the battle is fought by EU's. A 330 AM battle gives people the option of setting alarms, waking for the battle, and being sluggish at work. I'm all for the DEVS making all the battles prime time for the continent the server serves, but I would keep the reinforcement window tied to the attack launch time.
And they aren't cowardice. These attacks are launched on caravans. I realize it's a difficult concept for you to understand, but a lot of ground can get covered from 2 AM to 4 PM. Waiting around for a 'better' time could leave the attackers exposed in unfriendly territory, give the trader time to quick march away, or hide all together in a fief.