In VGC, Pokemon aren't just up and banned like in Smogon formats. In fact, it's only happened once where individual Pokemon are banned. In addition, the ruleset has been decided for the next 3 months so they wouldn't be banned until February, if at all. Kingdra + rain setter is a good core, but Politoed is much better than Pelipper. It's bulkier with a better typing, and has great support moves. You don't need tailwind because of Swift Swim. With Helping Hand Politoed and Life orb on Kingdra, Your matchup against Landorus and Dragapult is much better. You don't want ice beam since Max Hailstorm will overwrite the rain. Physical Kingdra is hard to pull off because of intimidate, special + life orb is much more useful because of access to hurricane. The problem with Duraludon is, It's got terrible special defense and it doesn't even hit Fini or Koko, the two most popular, for super effective.
There are a lot of interesting things you can do with rain, like Dragapult or a scarved U-turn pokemon U-turning into a Ludicolo to activate a weakness policy and bring in the rain setter in one fell swoop. Zapdos likes rain teams as well, with STAB Thunder and Hurricane. Stally Pokemon like Celesteela and Ferrothorn benefit from rain too, because it protects them from fire types. You'll want to have a gameplan for other weathers, namely sand and sun (Trick/Eject Button Sableye is cool- You have prankster rain dance to practically gauruntee weather control and can pivot out with the eject button into another sweeper), but I think your team could be a really strong rain team with just a few tweaks.