Just tried to upgrade mariadb again and got this:
You might want to run 'apt-get -f install' to correct these.
The following packages have unmet dependencies:
mariadb-galera-server-5.5 : Depends: mariadb-server-core-5.5 (>= 5.5.36+maria-1~wheezy) but it is not installed
Now I reverted back to
deb http://ftp.osuosl.org/pub/mariadb/mariadb-5.5.35/repo/debian/ wheezy main
and will keep on using it for this system. hopefully you will get mariadb added to debians official repo so it can get properly tested.