Please help I'm ready to rage quit over this swamp boss

This is my favorite soulslike Ive ever played. I am extremely enamored with it, and am therefore surprised that I have reached this point of frustration. If I had 10 hours a day to try this boss again and again until finally by some fluke I get him, that would be one thing, but I have shit to fucking do. This boss is water trash horse shit. Phase 1 is easy to get through. Phase 2 is the cheapest shit I've ever encountered in a game of this ilk. How THE FUCK are you guys getting through this?? My whole playthrough I've had my heart set on that two dragons sword, and now here I am.. stuck, for the first time in the game mind you, on the very boss I need to kill for it. This is so infuriating. Need serious advice.

My level is 64, I'm using puppet ripper +3 and a specter and buffing with fire. Legion arm aegis.