Shall we actually try to figure out this bug? We need more info from people it didn't work for.
It worked for me, so I can contribute a few things that do not cause the bug:
DOTs don't cause it. I had volatile accelerator equipped, and I definitely saw at least 1 enemy die on their own turn from DOT. Also for video evidence of this, BitDynasty's guide to the boss feat, you can clearly see enemies die to DOTs.
Instant defeat moves don't cause it. I used CAT in my squad. Used force leap to kill an enemy.
Having team members with the leader tag doesn't cause it. I used JMK lead, and team members included Shaak Ti and GMY. All of them have the leader tag.
I don't know what my full disk loadout was, it was a couple of days ago. Volatile accelerator, amplify agony, vitality, protection recovery is all I know for sure.