I did as you proposed and at first it seemed to work, as there was an error and after fixing it there were no more debuging errors:
But sadly it did not work...
mozork@mozbook:~$ killall devilspie
mozork@mozbook:~$ devilspie -d
Devil's Pie 0.17.1 starting...
/etc/devilspie doesn't exist
Could it be because I've named my workspaces other than workspace n. Or could there be any other reason why it is not working?
(is (application_name) "firefox-bin")