When i was level'n with my iksar monk i saw him bout 2 or 3 times a day....( i play alot...hey its summer) the only reason people seem to think he is rare is because this mob type is generally ignored since they often agro in groups are a pretty tough fight even for a group. Since the prowler shares a similar model with the other scaled wolves i would imagine he is just over looked. Keep an eye out for him and im sure you'll find him easily enough.
The prowler Jumped me last night while I was on the West Side of FoB. I was Fighting Scalebones and Giant Scorpions when it jumped me. I gues it is a random spawn. I got a Decent Cloak out of the fight. I did not know about this spawn and I am please It found me. I guess the only suggestion I can make is Hunt one area and stick to it. It might show up.
I was in the "pit" area just clearing it out when up pops the scaled prowler. It looks just like all the other scaled wolves. It dropped just the belt tho. It's placeholder I believe could be anything roaming around FoB.
I'm an iksar who spent level 1-20 here and continued to walk through this place untill level 25. I've not only hunted just about everywhere, but gone exploring near the Emerald Jungle and Kaesora looking for this, the burynai cutter, etc. I've never seen this thing and I'd like to go back to The good old FoB to take another look around