Mirtazapine is not an SSRI or SNRI. It is a NaSSA. It works differently than the others.

If the doses are so low as to be non-therapeutic, you should be able to stop them and see how you do. I think you are still getting 'shot in the dark' med care since nobody seems interested in giving your meds a serious look.

Being free of them with an occasional minimal dose benzo for emergency situations may be worth considering.