If you're having trouble getting something specific I would try different bosses that would also drop it, unless it's a unique item that only that boss drops. I've been farming for the Shoes of Houdini for 10 days. I've fought Underdog, MacCavity, and Bishop with no luck. Then I gave Red Fox Lair a shot and got it on my 3rd try. I personally think it's all random luck but I do notice certain classes get more of another classes No Auction gear than normal.
There seem to be better drops with multiple Pirates. Of course with multiple Pirates, there are more chests to have loot in along with Gold. This is good for all fights whether there are Bosses or not.
In that case, find a realm where you are constantly getting No Auction gear and stick with it. Last time I farmed Cadmus, I was getting an item every other or third battle. The Blades of Shade dropped again for me on my 50th fight, but I already had at least 25 No Auction clothing drops. You don't have to farm that much but I did because I was getting an awesome drop rate the time. Anyways, good luck finding those blades and, if it helps, I was in Blind Mew.
I have a question concerning loot tables from bosses. Do all bosses that drop similar gear(clothing as opposed to jewelry) of around the same level have similar loot tables with the exception of unique items?
For example: Cadmus drops Blades of Shade which are unique to him. However his clothing drops include items that I have received from Grohl, Minotaurs, and Antinous. I have been farming for the Crest of Faunus for several days with no luck. Now the wiki says that Cadmus drops it, however some people have said they receive it from Grohl. I have not seen anyone say they have received it from Minotaurs but I am assuming since all these bosses have the same loot table and kind of loot(clothing) that they would all drop it. Am I correct? Or are there other certain items that are specific to certain bosses?
I like the option of the second chance chest with Minotaurs so I would rather farm them, and Grohl is a lot less time consuming than Cadmus, so if I had to pick my farming I would say Minotaurs>Grohl>Cadmus; however I don't know for sure if the Mino's drop the Crest of Faunus. I know Cadmus does, and I THINK Grohl does.