Comment # 24 on bug 1008248 from Stefan Dirsch

Yeah. There is this bug in "localectl set-keymap", that it doesn't touch
/etc/X11/xorg.conf.d/00-keyboard.conf, if the keymap is already set in
/etc/vconsole.conf. :-( 

As a workaround you can change the value in /etc/vconsole.conf back to
"ch-de_nodeadkeys" and then run

  localectl set-keymap ch-de

manually. This should change the settings in /etc/vconsole.conf and
/etc/X11/xorg.conf.d/00-keyboard.conf to deadkeys. After a reboot at least new
users
should get the new default keyboard mapping.