I used to play a ranger on test server and I remember there being an underbrush brownie up basically all the time in Lesser Faydark.
I recently rolled a ranger and I've been looking for this guy but no luck.
I understand the spawn for this mob has recently been changed?
I read the following zam thread
http://everquest.allakhazam.com/db/item.html?item=1021
It seems to me the Underbrush don't have PHs and they spawn more or less five minutes after being killed (perhaps even instantly?).
I've been killing wasps, fairies and brownie scouts and none of these seem to be making thistle spawn. He is far more rare than that thread implies.