If your talking about the DR bonus, it really should only apply for full instants runs. Other wise se should kick off an "assist" reward for jumping in on a half finished run. Base it off of percentage of completion. Because do you honestly think its right to hop in half way threw a run and get full rewards? Having other folks sifting threw the mobs then pop in and get the reward for the entire run.

If I misunderstood anything I apologize.