Right now it's just not worth doing this in a group, because it takes too long for no real reward.
Sisters also give 1 Corrupted Holokey per sister defeated, so this isn't a new thing
appreciate the feedback here :) In a Hotfix coming later this week, we'll be adding additional Heartcell rewards for playing the Technocyte Coda Showdown with a squad! Players will get 1 additional Heartcell for every Coda defeated beyond the first - more rewards for more work! Happy hunting!