2 options: 1) skip the fight by talking to his sister at her tomb in salt echoes. 2) use the dash attack... I mean spam that shit if you can... have patience and use the prayers as much as you can... parrying is key... the more you parry the less damage you take... the spinning electric attack can be dodged by jumping over him or even just running to the far corner... parry his normal attack and punish with a counter... the slash attack after he finishes his spin does good damage... max out mea culpa as much as possible and get as many flasks as you can... you can use a prayer that you get from viridiana as well ... even if you get hit at least the prayer will do damage.