Hard to say with little detail on your rotation and gear. From my experience as others said practice of the fight helps a lot, but I saw no one really mention gear. Though we may not have official stat weights yet for RDM to work off, a single piece of gear being subpar for you could lead to lower numbers. Group composition, buffs use, and even yours and those you are doing run with mood can also as much play a factor. You of course can only control your own gear, rotation, and mood, but take a look at the group as a whole. It can play a lot into it as well.