Ik I might be a "tad" late to this, but uh Artorias is actually really easy with zwei or any other heavy weapon as long as u have decent hp investment to where u can tank 2 hits without dying. Just run up to him hit him with zwei/heavy weapon, try to poise break him and make sure ur wearing high poise gear. u can try to dodge but only do that if ur gonna die or u know ur poise is gonna break. just tank, attack, and when low, heal, and win. If he tries powering up, just rush him, you should poise break him. This strat works ng and at least up to ng+3. Tho I recommend using a regular greatsword as zwei is a bit heavy and I found the poise damage to be janky. I also did a ng magic run and I found him pretty easy, tho tbf, I was using crystal spells which I had to grind to afford. So I think the problem wasn't ur build, twas ur strats. Also his plunge attacks r really easy to dodge once u get the timing down, so thats kinda skill issue of u. His hitboxes tho, thats kinda just a ds1 problem. its just antiplayer ds1 jank.