I believe that one resets at 20:00. This is kind of good, since before, people would login at like 23:58 right after maintenance and sneak in an extra pull before the reset.
Now people might do that on the last day, though. Depending if there will be maintenance starting at 20:00 and taking until the next day.Samael's Hammer is pretty decent, yes. If you intend to invest into Dark, go ahead. Is there a reason for you to invest into Dark, though?