I think Qwilfish should be C-ranked. Although it's a great wall, it's mostly due to it's typing. It just so happens that Fire and Fighting tend to be the physical titans of UU, and Qwilfish possess the typing to counter the two--in addition to the ability Intimidate.
It's special bulk is pretty terrible, as it's taken out easily--even with resisted hits, such as scalds from Suicine and such. It does have a pretty awesome support movepool in thunder wave, taunt, and destiny bond (of course T-spikes and spikes); however, it's just a support mon and cannot really function well on its own. Therefore, I suggest C rank for Qwilfish.
It's special bulk is pretty terrible, as it's taken out easily--even with resisted hits, such as scalds from Suicine and such. It does have a pretty awesome support movepool in thunder wave, taunt, and destiny bond (of course T-spikes and spikes); however, it's just a support mon and cannot really function well on its own. Therefore, I suggest C rank for Qwilfish.