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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7 purple tonics to craft that is 28 flakes needed so 28 runs of the mission! Absolute crap!!