My penetrator strategy is pratically the same that Crystalchild gave you, except that now on NG+ you can't rely on Biorr at all, since he dies after a few hits of the penetrator.
I managed to defeat him without getting hit once, the main issue is mobility. He moves extremely slow, and all of his attacks are really predicatable.
If he puts his sword behind him, he's going to do a 360 swipe attack, when he does, wait for the moment that he does a small jump, roll forward and do the rolling attack. Roll backwards twice and you'll escape the subsequent attack.
If he has a white glow on the sword, roll backwards, that move is a OHKO. After he thrust the glowing sword you can run up to him to get one or two free hits, then roll backwards to escape.
Edit - His attacks are purely physical, Slash and Piercing if i'm not mistaken.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
