While the devs have done a good job of cleaning up the drop tables for netracells, they have completely overlooked tome mods and tennokai mods, which have absolutely atrocious drop rates from incredibly slow game modes, and were left untouched. Putting 8 mods into a single C rotation at only a 5% drop rate each means that it will take, on average, 50 C rotations for a player to acquire all 8 of the mods that they need, a 20 hour farm given the 24 minutes per rotation in both modes (technically alchemy could go faster, but it seems to on average be slower than survival).
At minimum, these drop tables should remove all of the other junk from the C rotation to give a 100% chance of getting one of the mods you need from each rotation, but even that would still leave an 8 hour farm. Something far more drastic will be needed to truly fix this issue, such as putting the drop chance into all rotations, not just the C rotation, or even just making the mods obtainable from alternate sources such as Sanctum vendors.