When you're looking at rdps, the damage gain associated with a Crit/DH buff belongs to the player who supplied the buff. The actual winners are jobs like SCH and BRD, assuming that their rdps hasn't been rebalanced around this.

Let's just say I'm very curious to see how this actually gets implemented, though. The ratio of crit multiplier gain to crit rate gain will determine what job comp the buff favours.