@Your Spiritual Liege
I would say all BL3 DLCs were good. The best one, for sure, was the Handsome Jackpot DLC, in terms of music, environments, enemies and storyline. Close second for me was Bounty of Blood, then followed by Fustercluck and Tentacles.
A lot of my favorite soundtracks come from Handsome Jackpot specifically, and the re-introduction of loaders and Hyperion locations were awesome additions. The Spendopticon reminded me a lot of Opportunity from BL2, and also the Hyperion Hub of Heroism from the Pre-Sequel. The designers really do a good job at taking the right amount of inspiration from their previous games, without making any carbon-copies.
Speaking of the Bounty DLC, it would be interesting to see Butcher Rose in the next Borderlands games. After you defeat her, she doesn't technically die and just disappears, meaning that it's very likely she'll come back later. In addition, the Ruiner was a really cool boss (despite it being very similar to the Warrior), and the locations were nice; the Japanese-Western aesthetic was especially eye-catching to me.
Fustercluck was a deeper dive into Krieg's character, which I found pretty fun overall. I really like the way Krieg is written; he basically just communicates normal, rational ideas through insanity-riddled metaphors. Fustercluck really reinforced this process with Sane Krieg producing the rational thoughts and Psycho Krieg communicating them in the most absurd way possible. On top of that, the exploration of Krieg's past was very interesting, and I especially liked the part where we explored the Hyperion laboratory, and looked into how Krieg became insane to begin with (Dr. Benedict should've been stronger, though).
Tentacles is last on the list, although I do consider it good. The Bounded were a cool faction, Mancubus was an awesome NPC (probably one of the best in the game) and I liked Gaige's reappearance, despite the fact I never played her in BL2 (only the original cast + Krieg).
All in all, the DLCs in BL3 were great, but just wished they were longer, like the BL2 DLCS were.