Add a pouch to ADL is the obvious way to go with this. Chance for up to 10 people to get an item from 1 kill. Add a chance for singles to drop from some other NMs throughout the zone too and you're golden.

In theory, all 18 members of the alliance can get a Riftdross per run (highly unlikely, but possible). And you could farm them until the cows come home, and get the whole trial done in a day.