Attuning definitely does not work.
7 guns now and not one are what I attuned.
So attuning doesn’t work or is so marginal as to be irrelevant.
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It doesn't work for me either. I have 1 weapon attuned the rest are deactivated, yet I still get all of them drop more times than the actual attuned weapon itself. Wish we could focus them, it would have made more sense.