The chrome dev tools are a decent substitute. There's a 'pretty print' button at the bottom (looks like this - {}) that expands the code and updates links to errors, etc. You still have a lot of functions named stuff like '_1cc', but it's somewhat workable.
The ArcGIS JavaScript unbuilt source is not available, and as far as I know has never been available.
There is a posting up at the ideas site for this suggestion though, so go upvote it and let's see what goes from there.
http://ideas.arcgis.com/ideaView?id=087E00000004JOzIAM
I always thought that code had already been minified. meaning the var names are obfuscated and comments have been removed. But hey, if they were available before then I agree.
I think we're talking about two different things, so my bad.