So I thought, what if we could use the new dye system to our need, and make our own old-styled black dye? After a couple days of trying to at least get something close to the old black dye, I managed to make something quite accurate.
Please note that this dye recipe has not been tested on every single armors, so I am not sure if it works with every characters. All I know is, I couldn't get it right on most Monk, Warrior and Ranger armors. Further testing would be required as it seems to only work on Necromancer sets (since they are naturally darker) and the Jester's cap.
Here's the recipe in question:
Another mix that works nicely on Necromancer armors is Blue and Yellow. It is similar to the recipe shown above but it actually has a more blueish shade to it.
(Sorry for the grammar mistakes, if there's any.)
Feedback and more images would be nice

Have fun!