Let's face it, having only the people that damage the boss receive rewards afterwards simply isn't fair. There's always one a-hole who grabs the axe and dives right into the boss' chamber as it's opening, killing it in under 3 seconds before anyone else has a chance to even see what the boss looks like. Everyone who contributed to the run should be given some reward from the boss, not just the one guy who hogged the final enemy all to himself.