There is no randomness involved in the amount of dust you receive, but there are some criteria:
- You must be the highest damage dealer to the creature, or;
- Be in a party with the highest damage dealer, near the creature when it dies and with a battle sign. You do not need to have attacked it and shared experience mode is not required.
You'll get 1-3 dusts for each stack, the creature has. All elligible players receive the same amount, which is not split but the same amount regardless of the number of players.