"Delayed Recovery" talent in Witcher 3

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.

This is because the the calculation is based on potion toxicity only. Using decoctions will make it impossible for this to work.