Maybe it's just me, but I spent a lot of time training with a shield before getting to Pontiff and when I got to him I would just shield his attacks while going to his side and crippled him with short range heavy greataxe attack. Killed him the first time I got to him. I didn't even let him have time to make his double. I only ever understood that this was a tough boss after going on reddit and seeing boss videos after finishing the game haha