As to a bare-bones DLL "cracker", have used this tool in the past (in days of re-skinning XP). As to an all-in-one plain language dll decrypter?? Dream on!!
To break down a DLL file, you need to have at least a basic understanding of the type of DLL file you are trying to unravel. Just because they use a common file-type, don't assume they are all the same... as they are not. Apart from the fact that I've never found a tool that is even capable of unravelling every DLL file thrown at it, to expect a "plain-text" interpretation of every such file is unrealistic. Know the basic context of the DLL file you are trying to tackle, then Google for a specific tool to meet your ends... there are many to be found :)