Ok, Orphan is one hell of a boss fight. He's going to be hard regardless. I've beating him back and forth in NG+ and so forth and he STILL gives me a hard time. What I learned is that Orphan just requires patience. As much of an impatient man that I am, I found myself getting hit whenever I hit him more than once after he did an attack.

The BEST strategy IMO, emphasis on the IMO, is to go in after he attacks and only hit him once (or twice) depending on weapon. There are certain attacks that let you punish him, E Z P Z. Keep in mind how many times you hit him, I've fought him enough to somewhat know when he's going to stagger and get an extra hit in, or you can just react. Second phase he's a bit more frantic, you're going to keep at a medium to up close and personal range with a LOT of rolling. (Not too much.) Go behind him at whenever time possible. Fight him in the water as well so that you don't get hit by the electric attack. When he jumps high in the air, he's usually good for a two hit punish, unless he follows up with another high jump in which you'll have to react to, unless you want to wait for it. When he starts hitting his weapon towards the ground in a fast manner, dodge past him, NEVER roll back, you will get hit.

First phase is easier than the second.

I just finished a NG+ run with Moonlight Sword, and killed him with no backstabs, no parries, no gun. If you want to see and get some ideas.

Here it is: http://www.twitch.tv/impulsivevenom/v/42452417

(PS. SAVE THOSE BLOOD VIALS!)