And yet, there are situations where complexity is a good thing. Antibiotic / chemotherapy / pesticide resistance, for instance. Much harder to become resistant to a complex cocktail of plant compounds than a single pure drug.
I'm convinced that the sensory qualities of herbs contribute to the conditioning of their active ingredients, though this would take a good bit of lab work to parse out the various contributions. Some background for this belief can be found in my IGMS column "The Placebo Files."
http://www.intergalacticmedicineshow.com/cgi-bin/mag.cgi?do=columns&vol=randall_hayes&article=014
Also, pumpernickel, which has a complex mixture of flavors, much tastier and healthier than a refined white flour bread that spikes your blood sugar through the roof.