Okay, this was a pretty interesting piece of DLC, especially in that it probably took me 10+ hours to complete, drove me to stall it for months at one point, and then hooked me back in for the last 5 days or so. I've clocked over 80 hours and I believe I'm done with the main game (activated all bonfires, killed all bosses). I'm playing on a 2012 laptop, but the performance is still >40fps in most areas at 720p, which feels really nice (got 60 on DS1, can't even play DSIII over 30fps).
Shulva is a pretty great area all around. The design, the triangular prism switches and the elevators, the architecture- it's really nice and memorable. The enemy knights are kind of meh, and I don't like the bugs. But oh well.
I fucking hate the Dragon Sanctum. The beginning area is a death trap until you clear it over and over and over, and the rest is just a mess. I hated the spiky room, I hated the traversal, I hated the Lair of the Imperfect, all of it. Though, admittedly, it got interesting after clearing the Sanctum, getting the Sanctum Key, and finding the third Shulva bonfire. The latter half, the descent into Dragon's Rest, was pretty great. Got invaded there by someone, tried to rain arrows on them, but I accidentally fell down and died, hahaha.
The Cave of the Dead is FUCKING ABSOLUTE SHITE. Of all the areas they could have recycled, I'm really baffled that they chose THE BLACK GULCH, literally the most frustrating, maddening and annoying area of the entire game. At least The Rotten took only 5-6 tries, the Graverobbers took me more than 40 tries (and Havel's outfit didn't deserve to be brought back that way). It felt satisfying to defeat them, but I hated the design.
Elena was the highest point of the DLC for me. Fun fight, interesting design, the lead-up to her is great. Took 10-15 tries or so. Downed Sinh on the first try, and besides the arena, that fight was really underwhelming.
On to the Brume Tower- from what I've seen of it, it is fucking amazing. Same goes for Frozen Eleum Loyce.