Have you already explored this possibility? While sm_cvar mp_tagging_scale does seem to work pretty well, I feel like there is still a bit a drag. Might it be because of it? Values of sm_cvar mp_tagging_scale above 20 don't seem to lower it any further (tried up to 255).
I confirm that after set "flinch_velocity_modifier_large" and "flinch_velocity_modifier_small" to 1 in items_game.txt, tagging is completely gone.