Anyway, I am not sure it is useful to install benchmarks in
/usr/share/doc/ruby-mysql2, so unless you have a strong opinion on this
matter, could you remove benchmark/* files from ruby-mysql2.examples?
(you can use wildcards and write simply 'examples/*' in that file, and
modify remove_rubygems_from_examples_and_benchmarks.patch accordingly?
A few more changes I would like you to implement in debian/control:
remove the line DM-Upload-Allowed:, since it has been deactivated, and
bump the Standards-Version: to 3.9.4, as it is the most recent version
(contrary to what lintian says).