After uninstalling dev-java/gradle-bin corresponding directory in /usr/share (eg. /usr/share/gradle-bin-2.11_rc1/) is not removed however its contents disappears. Observed for versions gradle-bin-2.10, gradle-bin-2.10_rc1, gradle-bin-2.11_rc1, gradle-bin-2.9.
I'm not able to reproduce this.
Florian could not reproduce it. gradle-bin-2.10 is no longer in the overlay nor in the tree. Please test and report, if the bug remains with current versions and reopen the ticket.