make it drp it now or then at every kill inside mission. make the same thing with tomb flake and tomb/contest of elders.
otherwise this is just absolutely garbage economic.
Edit: Bungie buffed the drops, 4 per normal run, 9 in expert (so I heard, I didn't play the mission after that).
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You are more than likely to get the drop you want want fron the mission than to get enough flakes to unlock the tonic for it This season has been a complete disaster , I have no hope for Heresy