"Delayed Recovery" talent in Witcher 3
Solution 1:
According to this thread:
I thought I could just get up 50%+ toxicity by using decoctions and then have an easy time staying above 70% but unfortunately this isn't the case, all the toxicity has to come from potions
I think this was intended by devs, otherwise you could abuse this skill by having powerful potions always up.
Solution 2:
This is because the the calculation is based on potion toxicity only. Using decoctions will make it impossible for this to work.