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
AutoCompress scans files evaluating their compressibility (or current compression ratio), and compresses them (or decompresses them) if they meet certain criteria; namely the date since modification, compression ratio, and file size.
ps: I have no idea what the author means by "decompress them if they meet criteria"
Update: There is also a note saying "compress using NTFS compression" on an earlier page -- not sure if we are even discussing standard file-compression here.
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.