http://i.imgur.com/BKQKYpY.png

530 is possible but essentially you have to fail the last phase really hard, or at least, have your group just stand around and let you DPS. (note there's another mnk in this run, but I was still doing DK). 491 is a decent parse, at least to me, but 500 is easily possible without extending the phase to remove the downtime.