... if a toxin is touted as one of the deadliest substances know...it ought to kill more easily.
Yeah, that is how I feel about it. In the REH story, this powder is supposed to take out a full grown lion with one sniff of the stuff. The D20 rules come no where near reflecting this.
One more thing: the term "poison" has been thrown around since 1st edition D&D. This is incorrect when referring to animals/creatures such as spiders, scorpions, snakes, etc.
All these creatures use "venom", not poison. The two things work differently.
A venomous animal usually has stinger, fangs, or whatever that deliver venom from sacs. Whereas a poisonous animal will only poison you if you ingest it in some way; eat it, lick it, etc.