Would you like an in-game parser?

[Ciri_Wolf]

Because this role is lacking in transparency compared to the other 2 roles.

With my DRK, how do you know I'm not just doing my aggro combo and not using any of my other abilities to dps?

[Legion88]

Why are only DPS players being called out?

Like KarstenS said before, DPS are missing transparency in ther main task.

The following is my own opinion and not a official statement.
Main task of tanks: Holding hate on all enemies, mitigating damage taken.
First is easy to prove: just a look on the enmity bars in the party list or the colored dot before the name in the party list. Second is not really poveable, demand for parsers.
Bonus task of tanks: dealing damage.
Damage is a sideproduct of many basic tank actions. Good tanks can maximize this bonus while reducing the overdoing in their main tasks.

Main task of healers: Recovering the party from damage taken, mitigating damage.
Easy to prove: no one died, so all is okay, mein task complete.
Bonus task of healers: dealing damage.
Healers can use their free times to switch into their damage stance or maximize this bonus by reducing their commitment in healing to the minimum.

Main task of DPS: doing damage (more then a compareable healer or tank)
No way to prove if a DPS is doing well or just bad. And just cause things are dying is no prove if a DPS is doing his main task.
I omitte the bonus task of DPS on this point.

With my DRK, how do you know I'm not just doing my aggro combo and not using any of my other abilities to dps?

You are talking about you don't bring the bonus you could do, fine, but don't forget DRKs "dps" skills are also mitigation skills...