If developers add achievements like that they should make the maps required.
Ive been searching in a party of 4 in Rumble pit for over an hour. And I have yet to find 4 other people out of 1600 who have Defiant. Its been out for 18 months! If you saved a dollar a month you still would have had it 8 months ago.
[Edited on 09.09.2012 2:49 PM PDT]