The character creation restrictions do seem to change throughout the day based on population, although some servers never seem to become unrestricted. I've noticed this as I've been trying to create a character on a particular EU server myself for the last 5 days.

For example, at the current time 24 of the 25 NA servers have character creation disabled, about 5-6 hours ago it was only 5. Approaching peak time in NA I guess.

Similarly at the moment only 1 of the 6 EU servers has character creation disabled (it's 2.30am here) but about 4 hours ago all 6 of the EU servers were closed to new character creation.

So the fact it varies does mean it's worth checking at like 3am, but as I say even then there are a number of servers in both NA and EU that it seems haven't had the restriction lifted at all in the last week or so (apart from, I think, a brief period after the update went live the other day.)