I couldn't find any good training spots after I got past the credits, so I stopped playing for a while.
I picked up the game a day or so ago and found Route 14.
Serperior - lv. 60
Reshiram - lv. 60
Victini - lv. 60
Simipour - lv. 60
Candlejack/Litwick - lv. 57
Tranquill - lv. 37
(the top four were under 56, Litwick 48, when I started)
I'm going to get Candlejack and Tranquill up to 60 before I continue exploring/training/beating Elite Four again.
Black City is so damn bare, I thought it would be huge immediately not periodically after doing something related to White Forest.