Just some general recommendations:
* Killing Ornstein first, makes the second part of the battle cake
* Get some pine resin/charcoal on your weapons for extra damage, if you can afford it
* Use the pillars as cover. They can hit you if you're standing next to them, but their pathfinding is shit and they'll get stuck and you can use that time to think, heal, cry, etc.
* If they kill you in two hits, your armor isn't really making any difference, so make sure you're able to roll super fast. The invincibility window in your roll is MUCH better
* Don't rush things, watch Orstein do his thing, and punish if you know it's a free hit. Take your time and you won't make mistakes.
* If all else fails, there's no shame in summoning help, even Solaire makes a world a difference. I did the first time.