What's the difference between the brock and wolf potions? They're both described as increasing critical effect chance for the same attributes but brock costs more and also has a negative effect. Wolf has no negative effects. It seems as if brock is redundant?
According to the Witcher Wiki:
As you can see, there is a difference between the two potions, and that is the resistance to ... the Brock potion has. To me, it seems redundant, as it's toxicity amount is high, and it should be used perhaps together with the Golden Oriole potion, to neutralize the Brock's negative effects.
In fact, the Wolf potion has as you said:
Seems like a game mechanic bug to me.
If you go the way of the alchemist there are some advantages to being poisoned. Also the negative effects of potions can be lessened/removed. Thus you might prefer to use a potion with higher toxicity if you specialize in alchemy.