Duty rewards tied to meeting a basic minimum performance requirement:

Nothing crazy to meet, but the Devs could set a standard for performance that a decently geared player at that level should be able to achieve. It would be different for each role as follows

TANKS Positive points for damage mitigation, avoiding avoidable damage, and holding aggro. Negative points for the opposite.

HEALERS Positive points for avoiding avoidable damage and healing group damage or shielding appropriately before attacks, clearing debuffs. Receive negative points for overhealing, gaining aggro, letting players die to debuffs (like Doom)

DPS Positive points for damage dealt, maintaining buffs, avoiding avoidable damage. Receive negative points for the opposite or stealing aggro.