there has been such project on wiki for long, they called it drop research. the problem is the sheer amount of things... there is thousands of skins, thousands of mobs and likely tens of thousands of bosses. these all would have to be tracked distinguishing by rarity of the drop (white/blue, purple, gold), level of the mob, and sometimes even different versions of the items (dyeable or not, small or big skin, dye pattern, etc.).
Problem really is collecting the data since everyone does mistakes, some things aren't checked, some are forgotten and some can't even be seen ingame...
I think a complete list would be awesome, but I don't see it coming as a community project. I wouldn't even know how to organize such list in a readable way - best would likely be a matrix with all the item versions (skin, dye info, rarity, insc/os) in the columns and all mob versions (name, level, area) in the rows. This would be a rather gigantic 10000x10000matrix (I am estimating here and might be too conservative). separating by campaign could eliminate quite some unnecessary areas (no insc items will drop anywhere in proph or fac for example, no daggers in proph, and so on) but it'd still be unmanageable - a screen would have to be posted for every entry, that shows all the specifics of the mob before death and all the specifics of the item after drop. else it'd be errorprone.
I might sound pessimistic, but I fear that is the truth. certainly some popular skins might get a completed list of where they drop, and there are other ways to group things... like core skins as one huge group - but even there... certain mechanics make that we'd have to distinguish plus we do not really know what core skins are. we'd have to compile the above matrix to some level of completion in order to properly group such items and THEN we could further conclude some drop locations. Also mobs can be grouped in categories - wiki articles on family, affiliationand species give some insight - and we are all familiar with the matter: outcasts, kappa, undead, ... they drop different trophies and some even have specific skins they drop (outcast items, kappa shields, and so on)... but again we'd have to first collect the entire data in order to properly group mobs into categories - and some don't even have a proper name...
I know there has been done work on different fronts and certainly there is more insights out there, but due to the amount of work that'd be put into it plus the benefits it yields I fear much wouldn't be shared publically - not lastly due to the risk of exploiting it (bots).
That is quite the number of variables. 
I certainly wasn't contemplating every drop, but to start with at least the popular things to farm/hunt down and that people like/find useful. To compile what is known already, should people want to share, rather than start from scratch and try to capture new droprate data.
There certainly seems to be a fair amount of those things that are known already.
