Probably still Io, thats what I used.

IO.

And it will take a while, even with boosters.

I'm grinding the 7000+ needed for the Itzal research myself, so i'll see you planetside,,, :D

i did farm ~120k oxium the last weeks for my dojo decorations and tried many different missions. best outcome was still with Io. (I always use Nekros + both boosters for resource farming)

My drops were always between 700-1400 oxium for 10 waves. (Depends on the team, sometimes i met Hydroid and another Nekros in the same run, then it spiked to ~2500 oxium for 10 waves). I talk about 10 waves of Io, because most of the time ppl leave at 10 and from 10 onwards there will be more eximus units and (in my opinion) fewer oxium drones.

I tried a lot of Helminth shenanigans and my most favourite skill for my ranged loot nekros on Io is nidus' Larva. And then i slash the dumplings with my sword.

I don't think Nekros's desecrate works on oxium drones because they done leave behind a body , they just blow up right?