All the kids with their safe spaces think "hey healer, how about you actually dps instead of picking your nose" is harassment? Seems bullies these days are slacking that you people got your definition wrong.

You job in a group
*To perform to the best of your ability in order to ensure your group as a whole has a good experience.

Failure to complete the above can be defined as:
Sitting around afk waiting for damage to happen
Using an ability every 5 seconds as a dps sitting at full resource and doing half the damage you are capable of
Not using your defensive cooldowns expecting the healer to simply heal harder

An in game parser may lead to harassment. But there needs to be some incentive for the slackers to actually improve.
An activity monitor in combat that disqualifies a person for loot for low active time. There is ALWAYS something to cast, a button to hit. A monitor showing less than 75% activity would be a good way to filter these leeches out.