Don't be fooled by thinking salvia is just a "legal high". It can cause profound ego-loss for upwards of ten minutes. The history is that it is what native american shamans used to chew on to see visions.
A common experience is one in which people say "I forgot that I was something, then I realized I was something but I wasn't sure what that was." They then had to figure out the world again as the drug wore off. I think it's foolish to group something this psychologically powerful within the same group as something that "just gets you high" like alcohol or pot.
You're right that it's much more powerful than alcohol/pot but the truth is that it is legal in most countries and states. The "upside" is that its effects totally wear off after ~15 minutes and there are no known long term or addictive effects.
The fact that some drugs are legal certainly doesn't mean they're not as strong or powerful than ones that are illegal. Salvia is, apparently, one of the strongest hallucinogens there is. The difference between it and, say, LSD, is that the Salvia "trip" only lasts ten to twenty minutes. I have personally tried Salvia some years back and have had some seriously bizzare experiences. I'd rather not post them online, but if you're interested, send me an email.
Cool! How did you set up the double-blind study?