On my country St Johns wort is vey used by folks on small towns an d villages. I have clinical experience of patients that had indeed improved, some have not of course.
My honest opinion is the next. Allopatic meidicine is nautral medicine, the only difference is that allopatinc drugs are measured and graduated.
To make my point i love to use the digoxin example. The digitalis plant from which the drug is extracted was known as a poison since middle age. Careful observation of its effects derived on its medical uses. The British physician William Withering is credited with the first published description of the use of digitalis derivatives in his 1785 book "An Account of the Foxglove and some of its Medical Uses With Practical Remarks on Dropsy and Other Diseases".
Nowadays we do no go to a hill to attenpt to produce a tea with the plant, it will be too risky. The best option is going to the drugstore with a prescription and take a pill that has exactly 0.125 mg of the drug. With the proper follow up and regular digoxin serum concentration test we can be sure that we can have the benefits of the plant with a low risks.
One more thing, the problems with drugs concentrations in less dangerious plants is that it is highly variable. Many factors alter the concentrations for example quantity of rain on the season, quality of the soil, use of pesticides, transportaion and almacenation postcultivation, process of comercialization, etc...
So finally, i think the best bet are allopatic drugs with the proper medical follow up.