Ok so I just managed to do this first try, amazingly. After reading all this, I was pretty sure I was gonna get my***** pushed in and fail and Eileen would be dead and everything. So I tried visceraling him + a charged attack from transformed weapon. It worked but did like no damage, so I was panicking at that point. Then Eileen comes in and at first she didn't do anything, I used the Gascoigne strategy with the tombstones which was working well, I got him down to probabbly 1/2 health. Then he realized that this was now 2v1 instead of 1v1 and goes after Eileen and I used poison knives and my pistol as covering fire while Eileen laid into him and I had to kite him around a bit but he went down before I knew it. Overall, it was heart-pounding but not as difficult as I thought it would be after reading all this.