Just finished everything, spent about 40 hrs total, 6 on the final boss lol.
10/10 DLC until that final boss. I finally admitted defeat and used a spirit ash (mimic) for the first time ever in the game. Seriously, the difficulty spike is beyond anything I've seen in a souls game. What's truly annoying to me is that using the mimic tear, I beat it on the second try after 6 hours of trying solo. Never really was able to learn any of the patterns in the second phase.
That aside, some of the best area designs in the game are in the DLC. Especially liked Ruah ruins. I do wish there was one more "legacy dungeon" style area (beyond Messmer's castle), but can't really complain— some came close, but ended up being pretty small. Some really good bosses too. Unfortunately no new weapons that really tickled my fancy.