Reading this thread got me piqued to farm this Amulet. I got it years ago, before I knew what it was, and got rid of it.
It only took me three runs. The first run did not spawn Moontooth Dreadshark. The second run spawned it, but it did not drop The Murlocket. The third run spawned Moontooth Dreadshark and it dropped The Murlocket! 
Moontooth Dreadshark
You can tell when it’s going to spawn. You’ll find a pile of trash that looks like the usual hostile, breakable trash in these Dungeons (red highlight when moused-over). Except this pile of trash does not highlight nor can it be destroyed. However, when you approach it, Moontooth Dreadshark breaks out and attacks you.
I’m currently putting together a video of my session. It will be up shortly, (if anyone’s interested I’ll post a link).