Just finished a massive Darkwraith Knight grind getting all my armor to +9 and all my weapons to +14 and thought I'd share some (maybe) interesting stats and experiences.
I took advantage of the route and also farmed the necessary Dragon Scales to upgrade all the dragon weapons to +5 from the Drakes for the first part of my grind. I finished that about 1/3 of the way through.
Strategy: I used a Great Club +15 at 40 STR which one-shots them on NG with any two-handed attack. I used the Silver Serpent Ring & Symbol of Avarice to boost my souls earned and 10 humanity to get to 410 Item Discovery. I started with a few pieces of Havel's on staying under 50% weight so I would mid-roll. At some point I stripped down to minimum poise so I could fast roll/sprint to try and improve my run time, but I was a lot more inconsistent having some runs that took much longer and some that were shorter. My average time ended up being worse and I ended up putting the armor back on pretty shortly. Somewhere around halfway, I started using Sunlight Blade after the first knight before encountering the one right outside the shack so that I could get the overkill souls bonus for 6/10 of them per trip.
I didn't use any transient curses and ignored the ghosts. When you get to the room with them, you can run in and hug the right side, take out the first knight with a running attack and the second one should come up either in front or behind you around the column and you can smash him with an R1. If you go quickly enough, the ghosts should just be getting into the room and you can roll/sprint out the door, quickly turn right to dispatch the last knight then run along the wall toward the ledge so you can put enough distance between you and them to homeward/bone.
Now for some stats because I had to do something to keep myself occupied and interested:
Total active grinding time: 19 hours, 7 minutes
Total trips: 354
Trips w/ Drakes: 105
Trips w/o Drakes: 249
Average trip time (w/ Drakes): 4 min 0 s
Average trip time (w/o Drakes): 2 min 55 s
Total Darkwraith Knight kills: 3,534
Total Drake kills: 530
Total titanite Chunks: 1,026
Chunk x1: 956 (6.6% raw drop rate)
Chunk x2 drops: 35 (0.24% raw drop rate)
titanite Slabs: 20 (0.14% raw drop rate)
Dark Hands: 125 (0.86% raw drop rate)
Dragon Scales (from Drakes): 76 (3.5% raw drop rate)
I find it interesting that when accounting for what should be a 4.1x increased drop chance from 410 Item Discovery (raw drop rates), all of my drop rates were ~75% lower than the stated drop rates. Maybe this means nothing since the sample size isn't infinite and I might just be unlucky, maybe this means that the effects of Item Discovery are not linear like I have read it to be (i.e. 410 gives less than 4.1x increase), maybe the listed drop rates were determined with empirical testing that was inaccurate or has changed with a patch; I really don't know but I found it interesting. To match the listed drop rates on average, I would have to have around a 3.08x multiplier from my Item Discovery and there wasn't a lot of variance from that number between each item, so I'm leaning toward non-linearity or different scaling of the Item Discovery stat than I thought I understood.
Total souls gained: 7,237,032
Number of Darkwraith Knights overkilled for bonus souls: 1,064
SL increased from: 141 -> 176
Number of humanity lost from Dark Hand grab attacks: 4
5 Evil Vagrants killed
1 Red Evil Vagrant killed
It's interesting that there happens to be an Evil Vagrant spawn point past the corner of the building next to the ledge that drops down to the main entrance gates where the Drakes are. Since I was running over there to cast homeward, I saw a surprising number of Vagrants. I only missed out on one (I died to the ghosts because I was freaking out), so I saw 7 total over 19 hours. I hadn't seen any before this in my 150+ hours in game, so maybe people were actively spawning them or maybe people die farming here often and lose their humanity, idk.