While using the unpack feather of the dependecy plug-in we did searched and tried hard to get the 'excludes' option to work.
But whatever we did we were not able to get it working. Then came to the idea, of trying it with another archive type. So when using some zip file, it immediately worked. So it seams that somewhere in the unpacking of tar.gz, the excludes are forgotten.
Sorry, did not find time yet to have a detailed look into the code, to track where it happens.
PS: Also the documentation can be improved, where to include the 'excludes' tag. Under the tag 'configuration', or under the tag 'artifactItem'.
The plug-in configuration as we are using it: