Vizunah Square mission is were it's at. But you can't truly solo farm or duo, as it's a co-operative mission. Besides having to babysit Togo and Mhenlo, you will need some backup.
soloing the naga around eredon terrace has always done it for me. the odds of a consistant monstrous farm are slim. having said that i just use the sin solo (sliver) and go go naga slaughter!!
not to derail this thread, but do you mean to tell me you are pickin up as many as 20 fangs/claws/eyes per run? if so i need to spend more time on the island. as for everything in this thread they are all correct. pick any non human creature that is easily farmed and go nuts. if you can find them on the island that makes things much easier for obvious reasons.
Thanks for all the replies everyone. I'll bring my Rit out of hibernation for some farming & salvaging the items that could contain them too & also take my 600/Smite for a spin.