Is it a boss that you want in the middle? Delay it until after all your other off GCDs, DA > Salt(I sometimes place this after Unmend depending on the boss) > Unmend(back up slightly depending on the boss) > CnS > Scourge > Dark Pass > Low Blow > Hard Slash > (Plunge or relevant off GCDs)

Plunge is pretty poor in terms of using it in an opener due to the DRG Jump-tier animation lock that only makes room for itself, instead of 2 off GCDs.