Luck still does do something in DMS... just nothing beneficial for the group~
Depending on the other rings you were using at the time, I would agree or disagree with them~
That said, FF is more-okay to bring if you're in a higher CL group... and can still cover the buffs/debuff you're assigned. As well as being able to do decent damage/heal somewhat~
As of this time, you can't obtain it in any way. If you had no CL 10 rings on September 3rd, 2011 when they did the check, you're out of luck~
No clue if they will release it in some other form or not... but I'll say don't get your hopes up~