From the most basic and fundamental game design standpoint, an objective analysis of this game's trinity system STRONGLY implies that all jobs are actually at their core framework, damage dealers. The only differences between DPS, healers, and tanks is where the added responsibility lies:
DPS:
-deal damage with a complicated rotation
-master the complex rotation to maximize damage
Healers
-deal damage with a simple rotation
-keep everyone alive
Tanks
-deal damage with a simple rotation
-hold aggro and mitigate damage
DPS are pure damage dealers that have a more complex rotation as an added role mechanic.
Healers are hybrid damage dealers that have a simpler rotation to accomodate their healing duties.
Tanks are hybrid damage dealers that have a simpler rotation to accomodate their tanking duties.
Nobody is aiming to out-DPS DPS jobs. We're aiming to maximize our potential damage, with is around 1/2 to 2/3rds of what DPS are capable of, and generally it has always been balanced at about that ratio, so tanks are accustomed to it and we don't want it to go any lower than that. Not sure what about that concept is hard to empathize with.
