with mutter-3.16.1.1 installed gnome-shell-3.14 neither runs or builds. The result is that gdm hangs with black screens on logout or reboot and gnome hangs if started with startx. Let me know if you need a build log. You probably have to release gnome-shell-3.16x before releasing mutter-3.16.1.1
+ 19 Apr 2015; Alexandre Rostovtsev <tetromino@gentoo.org> + gnome-shell-3.14.3.ebuild, gnome-shell-3.14.4.ebuild: + Lock mutter dependency to 3.14.x (bug #547034, thanks to Harris Landgarten)