Why would you ban the move? It would just become NUBL. Otherwise we could have what ever pokemon we wanted in any tier if we banned enough moves.
There are options for switch ins against a +2 qwilfish with Quagsire, defensive Qwilfish, haze Golbat ( no rocks of course ). It's also easily revenge killed by a number of special attackers due to its poor special bulk.
Theres an off meta option with Eviolite Metang.
Not justifying it just adding other possible options.
Edit: Also forgot about Ferroseed which would be able to take some pretty serious hits from Qwil and retaliate with a mix of leech seed, gyro ball, and iron barbs.