Blizzard has done a very good job making Diablo 3 pretty much crack proof. That's right, although most people still think everything can be cracked, there are things you can do to your software to make it uncrackable. One of these things is hosting part of the program on your server, just like Diablo 3 did. Every time you kill a monster for example, the game contacts the server and the server responds back with the loot drops.
As you all know already, even the single player mode in Diablo 3 uses this client-to-server connection, so not even the single player can ever be cracked.
One way to "crack" Diablo 3 would be to use some sort of server emulation, ie. creating an application that emulates the Diablo 3 server and your client would contact this server rather than the real one. But still, there is no way to get the "real" values that are stored on the Blizzard server, so even server emulation will not be 100% accurate.
In case you are still waiting for a Diablo 3 Crack, take my advice and do yourself a favor, get the real thing: