Depends on the variety as to the potency & effect.
Also who cares if it's herbal? Your post implies herbal or extracts of herbs are weak?
There's lots of drugs that are herbal that are quite if not extremely potent.
IE. Ibogaine, or Ayahuasca (Banisteriopsis caapi vine with other "herbs") both of which are potent hallucinogens.
I've taken Kratom varieties at doses I found to be I'd say equipotent to a 30mg Oxycodone.
In fact I've taken just plain leaf that may have even been stronger than that, let alone the extracts.
I mean 7-Hydroxymitragynine is just one of it's constituents & that is found to be more potent than morphine using pD (2) values.
And kratom contains various other alkaloids besides just 7-Hydroxymitragynine & Mitragynine, as such it can be quite potent.
Really varies on the strain, the freshness & the like.
Extracts can be considerably stronger than plain leaf, but I've found plain leaf to usually be a better value.
You really need to be more specific in your question if you want a more specific answer though.
