perhaps it has something to do with the dosage? while LSD is extremely potent by weight...while mescaline is not...you need around 300mg for decent effects..and thats a lot of material to work with...now lsd..you only need say 120mics for effects...there isnt much room for messing up the dose...and also 5-meo-dmt is extremely potent and fast acting when smoked...5-10mg for a strong experience..there again there isnt much room for messing up the dose..

what is interesting though is that mushrooms...are far more easy to measure...BUT since the actives cant be measured by weighing the mushroom..you really have no idea how much psilo you are getting..

so its seems like the reason LSD and mushrooms are more likely to cause a bad reaction may be because of dosage...you cant tell how much LSD is on blotter...and you cant tell how much psilo is in a mushroom...

those are my two cents