Just a quick note, the Ḥashshāshīn using hashish is actually very debated. Similarly, it is very unlikely that any fighters would go into battle on a drug high, either from mushrooms, alcohol. They would more likely dance themselves into a frenzy of sorts. Think back to any time you were drunk or high etc. Could you honestly tell me you were an effective human at that stage? Could you really engage in a battle? If your a berserker, your the first into battle by the way after the skirmishers have softened the enemy up, so you would want to be a damn good fighter.
I’m not saying it never happened because there is a good chance it did happen, just that it was not the norm.
Alchemy should not be used in the game as a combat booster. Instead I think it should be used like it was in the 15th century, to create healing salves to cure your wounds, not to help someone make more. There were plenty of herb pastes, oil balms and wacky creations that the people used to “cure” their wounds, something as simply has putting honey compress on a wound would work wonders as it is anti bacterial but all these things would be seen as alternative medicines now days…