Faust actually has a fair amount moves that are reversal-safe meaty against Johnny's super. 2K, 5P, c.S, 2P, Air FB>SpringBack. And a number of normals that he can reversal between the superfreeze and the active hit. Dust being one of them, as well as: 6P and 2S, and GambleSuper and crouchwalk.
Wakeup super against Faust is an all around bad idea. Faust doesn't have any reason to give Johnny a wakeup super.
Faust's 6P is one of the weaker 6P's in the game. The invincibility cuts short before its active frames. But people get hit by it 'cause they're trying to deal with 2K and 2S, and sometimes 5P. KillerJoker is indeed Johnny's anti anti-air, but it doesn't work too well against Faust's 2K. DivineBlade is Johnny's almost-absolute anti anti-air, but the rewards off it are significantly less.