Defiled Chalice pain

Trying to get the Platinum, so I’m going through the Chalice dungeons.

Fighting Defiled Watchdog on a 99 Arcane character in NG+1 with my main upgraded weapon (LHB) using fire gems (and the other being the tonitrus which has pretty bad reach). Fire dog not weak to fire.

The fight itself is pretty straightforward but oh my God I will never kill this boss, I do like 100 damage a hit even if I switch to tempering gems on my LHB

Please tell me if there is a better way to do what I’m doing.

Edit: hunter tools my beloved. for anyone else reading this, i used a call beyond and melted watchdog, as well as killing defiled amygdala on my first attempt