If that were true, there would be as many tank as there are DPS. Thing is playing a tank is much more stressful than playing a DPS, especially in dungeons (and not so much in raid). Because as a tank it is you who is giving the tempo in a dungeon (group (deciding when to pull and how much, and handling huge packs if the team wants you to make big pulls).
As a DPS, you only have to follow, execute your single target/AOE rotation, without thinking too much.
That aside, I don't really care about tanks rewards or whatever, but I think if SE wanted to fix the issue then they d just do stuff like in wow and would give DPS some way to tank (with specializationq or whatever). Also, if you feel like there is a need for a' reward 'for you to play then you should ask yourself if you're trully having fun playing the game.
