Diablo® III

I have noticed that as I have been playing it is difficult to get enough tomes to keep up with the essences that have been dropping and I'm not even crafting shoulders (got lucky on my first craft).

There are probably many others out there experiencing the same issue as me.

Additionally there are those that aren't interested in crafting or that are satisfied with their current crafts.

In these situations Demonic Essences become another useless drop for us.

Solution:
Introduce a vendor/trader that you can give Demonic Essences to in exchange for Tomes of Secrets/Exquisite Essences/Iridescent Tears/Gems. (qty per essence TBD)

Put the vendor in Act IV and only make him available once Diablo is killed.

I just think tomes need to drop at a slightly higher rate; I suppose a reduced cost in tomes would work, too, but it would be harder to balance. I'm constantly short of mats, though, so I have a biased opinion