Dropped this morning. I have been going to PoM hoping to find The Mischievous Jester up for a bit. Got lucky, he was up! And Bristlebane was kind enough to drop the shrinker :)
Have gotten 3 of these to drop fairly close together recently. One for my main cleric and 2 more for some guildies. I think the first one dropped on my 5th kill. The other 2 dropped back to back on the 8th and 9th kill. Doesn't seem to be overly rare in my experience. Much, much more common and less of a headache than the DoD zone-wide rare one. I think I went through 45+ missions before giving up on that one and going for this instead. So glad I did now.
May 5th, 2009 on the umpteenth kill, It finally dropped. I was ready to give up, thinking it may have been nerfed at some point. Now, the only time I have to see Bristlebane, is when someone pops a jester.lol