Yeah, the durability is like a tell.
Failed uniq or failed set happens when the game fails to generate a uniq or set item for some reason. Failed Uniqs spawn as Rare items with x3 durability and failed Sets spawn as Magic items with x2 durability. This can happen for a few reasons...
* Either there is no Uniq or Set of that item type. Scarab Husk is a good example. Has no Uniq nor Set version.
* The monster can drop the base item but not the Uniq/Set item. This is the most likely case and the case with the Corona in my picture. Had this particular roll dropped from a Boss Pack or Champion pack it would've been a Crown of Ages.
* A uniq item of that type has already dropped in that game (you can't have two Uniq items of the same type drop in the same game).
Should also be said that this can happen with rings, amus and jewels but there's just no way to tell since they have no durability.
The game checks: TC (Treasure Class) > Item (through magic find) > Item Quality > Item Stats
So it's lilke: TC 87 (monsters in level 85 areas can drop ANY item but not their uniq/set versions) > Corona > Uniq (but monsterlevel is only 85 and CoA is TC 87 so failed uniq) > Rare (with x3 durability) > Stats on the Rare Corona
This is also why you should get as much magic find as possible when running level 85 areas. It's not like when you farm Andariel or Mephisto where mf sooner or later doesn't help you. And this is where you have to weigh in all other factors. Kill Speed, in HC you have safety, area to run etc. There are no simple answers where to mf or where to farm stuff, it depends on your char and setup but most importantly what you are after. Runes, lower TC items, higher TC items, socketed items etc.
Then there's mf breakpoints aswell. (250*MF)/(250+MF) is the formula for those. It's not very important since the breakpoints are very stacked (ie 298 > 304 > 309 etc...) but it might be good to know if you need that last small charm or not

One thing is very certain though, for the high end items in higher TCs, level 85 areas and possibly Pindleskin are the best places to farm. Get high mf and kill only bosses/champion packs and their minions and sooner or later the CoA, DWeb, DFathom or whatever is yours.
And I just strayed off a very simple question, sry sry
