I don't know about you, but I've found Slowking is probably one of the best pivots for offensive teams. Being able to cushion a lot of blows from both sides of the spectrum with a physically defensive spread, and having Thunder Wave and Dragon Tail make for an amazing paralysis shuffler, which is something Slowbro really wishes it had—it also wishes it's tail wasn't being bitten by a Shellder, but that's another subject. While it's true that without offensive investment Slowking's power is lacking, Scald's burn chance and the ability to prevent stuff from setting up on it—with the obvious exceptions of SubRoost Zapdos and SubCM Raikou—more than make up for its lack of offensive presence. It also makes a great pair with SpD Rhyperior, which takes on Electric-types and physical Fire-types for Slowking, while also phazing with Roar/Dragon Tail.
The spread I was using in my latest team was 248 HP / 12 Atk / 120 Def / 128 SpD Sassy to take on Specially-based MixVictini, the Nidos, and any Kingdra variant while being able to survive two Flare Blitzes from Scarf Darmanitan after SR. I didn't invest more into physical defense because I figured most stuff was checked by other members of my team—also since Mienshao, Darm, and physical Vic all have U-turn, King isn't the best first switch into them unlike Slowbro. I do struggle a little with LO Mienshao, but provided I keep Slowking healthy until lategame I can beat it mano a mano. Oh, the moves used were the standard, Thunder Wave / Scald / Slack Off / Dragon Tail.
Durant is a completely different subject, since when I built my team I needed a reliable answer to SD Weavile and Flygon. My first thought was obviously Escavalier, but the team I'd constructed already wasn't fast enough, and I needed a Scarfer so I took cim's—weird at first—suggestion of using Scarf Swarm Durant. I have to say that it's pretty cool lategame when stuff is weakened, since it's faster than everything except Scarf Timid Raikou. Spamming Iron Head along with the flinch chance is really nice, too. However, the lack of power is extremely annoying sometimes, since it has base 109 Attack and only 80 bp STAB moves, just too weak. I could use Hustle, but I never recommend inaccurate spamming moves in sweepers, and missing with a revenge killer is one of the worst stuff that can happen.
Oh, my set was 252 Atk / 4 Def / 252 Spe Jolly with Iron Head / X-Scissor / Rock Slide / Superpower.
I posted all my thoughts from my experience with these Pokemon, but I don't think I'll be joining this research week because I'd have to make a new alt and, frankly, I hate laddering lol.