This week, when we tried Mythos for dinner, it was closing at 4:30pm, so call ahead to double check.
The next day however, we walked in and only had to wait 25 minutes for a table at 11:30 for lunch. I would say they are slightly less crowded due to people wanting to try Three Broomsticks for lunch, or are stuck in line waiting to get into WWoHP.
If WWoHP is your goal, and you can't get in really early to be one of the first in line, don't make Mythos reservations you may not be able to keep.