I've always seen only 1 in the AH, and was kinda put off by the fact that it was only DMG 31 on Windsday. I purchased one last night, and all I can say is I'm impressed. It wasn't Windsday when I was using it, but it seemed like "every" second or third hit was a critical....and when Windsday came around...this thing turns into a BEAST! Don't sleep on this dagger if you can do the quest or it's in your AH.
Uncapped Balista: Mighty Knife & Garuda's Dagger = mages with brown stains developing in their trousers.