I went this past Thursday, and it was absolutely dead. It would be a great time to go. I got all 7 mazes, a ride on Ninja, and 2 rides on Wonder Woman all
90 minutes. Plus, the haunted maze pass is on $25 on Thursdays (it's $30 on Fridays and I think Sundays, and $40 on Saturdays).
And if you have a legacy Diamond Elite/VIP pass, they still do Preferred Parking, Diamond Elite entrance, and Early Entry (and free haunt wristband). I arrived to park at 6:15 (it doesn't open until 7 on Thursdays), went through and already saw a line to enter the park, so I suspect they open parking at 6pm. And the line to enter the park was only because security wasn't ready yet. Security was ready by about 6:30, and the line mostly just sailed through once open.
And best yet, nearly all of the mazes were still fully staffed with scareactors! Even Truth or Dare had BOTH flyer positions going, which I haven't seen in ages. The only maze that did feel understaffed was Saw, oddly enough. Carnage was packed full of scareactors, even though I was basically the only person in it, haha!
Only major downside is that since gates don't really open until 7, there's no real opening ceremony. But Margo and Slider shows still happen. Get there on a Thursday if you can! It's crazy you can do 7 mazes in the time it takes for one HHN maze