Every DPS class will tell you that their class is the most difficult to master and to a degree they're all right. Every DPS/tank/Healer job requires a certain level of understanding the nuances of the that specific job to be at maximum effectiveness. Not only that, you have to understand how to fight alongside other DPS jobs to stay effective. As a DRG my tactics to how I approach fight can change depending what other DPS alongside of me. My rotation focus changes when paired with a BRD, compared to a BLM.