Is there a compression tool which doesn't attempt to compress incompressible files in order to reduce the compression time? It would need operate on a folder (rather than on a single tar file), and it would try compressing each file, and give up if it doesn't make much progress. By 'give up' I mean switch to lowest compression level for that file.
Curiously there is AutoCompress
ps: I have no idea what the author means by "decompress them if they meet criteria"
In general, I think that 'compressibility' of a file might be estimated with some methods but they would imply extra time-overhead. There should however be ways to code the compressor so that it will 'bail-out' and just archive the file as-is with a mark describing that on it. While I like the idea, I've not yet seen this.