Im sorry i don't quite follow what you're trying to say, its not very clear.
you complain quite expressly about poor drops of bomb ash in your opening post and most everyone in the thread has disputed this.
What exactly is the issue you are having?
You say this isnt a mob that is meant to be farmed, but it drops an item people need and the monster in an area in abundance (around 18 pops in nanawa)
Is there a quest that requests bomb ash that tells people to goto nanawa to farm these for bomb ash? if there is, it doesnt mean that nobody else should ever farm here, if anything its a little clue to player base "hey guy, you can get bomb ash here"
if theres something else, please exlpain and i'll try to answer as best i can
::EDIT::
sorry my post was slow im at work and it took a long time to write.
Just because a mob is a quest mob does not mean it can serve no other purpose. the nanawa bombs are for farming as much as anything else.