The main issue is that all regions need to be down at same time, which is not convenient for us European players since we usually get the short end of the stick. Obviously, if the time for the updates was inconveniencing other regions, that would still be bad.
Another thing to consider is the time needed for this bugfix. 5 and a half hours, at time of writing, is an unacceptable amount of time no matter the size of the development team.
And finally, this is a subscription-based game. Any time you can’t log in because the servers are down is time you paid for and didn’t get to use.