Cap the Maximum Action Speed Penalty
Currently Thanatophobia, Hex: Pentimento, Scourge Hook: Gift of Pain and Dying Light all stack their penalties together to create truly absurd action penalties. I'm not exactly sure on the math but it looks like the these penalties can be stacked together to reduce survivors effective action speed to -50% or worse. If a survivor can only work on a gen at 50% effectiveness then that gen is going to take 180 seconds and I believe that is too harsh.
I suggest capping the Maximum Action Speed Penalty at -30%. Even at -30% it takes a survivor working alone 128 seconds to complete a generator which is still very punishing. This would stop Legions and Plagues from using these 4 perks as a build to make the game almost unwinnable for survivors. Then Thanatophobia could return to 5/10/15/20 and not be so oppressive and be useful on all killers again.
I also think Hex: Pentimento might be a bit too strong being able to hit this cap on it's own with just one stack but whatever. Survivors can just get off their gen and check on that totem over there they just cleansed.
On the flip side also think maximum healing speeds should be capped at +100% so heals would always take at least 8 seconds.