In the case of responsibly and professionally blended “100% natural” herbal smoking mixtures: Yes. Overall the herbal smoking blend industry has a good track record for safety ( other than the negative health effects known to be associated with smoking ) when the products are used as directed by healthy adults. There a very few herbs that do not come with some warning for pregnant or nursing women and people with health problems. These people should consult their doctor before smoking any substance.
Safer than Tobacco?
It depends on how you look at this. The fact of the matter is, although many people find herbal blends enjoyable and relaxing, they have ( in most cases ) not shown to be habit forming. So, in that respect, they are safer because it is less likely the act of smoking herbs will become habit forming.
As far as smoking herbs being safer to smoke than tobacco, we simply do not have enough scientific evidence to be able to answer that. We have seen research that showed particular herbs and blends produce less tar than tobacco when burned. We do know that, when smoked, herbs produce tar and carbon monoxide, which is known to have negative side effects. This leads to reason that the habitual smoking of any substance is likely to be unhealthy.