Thanks for the presentation, Stone_Cold! Interesting team, especially your choice of DNite (I was expecting LO Rain-Mix).
Just like ShakeItUp and me, you may want to try out Hypnosis on ScarfToed. 60% may be chancy for you, but it helped me out. Whether it be Latias, Gastrodon, Jellicent, or Ferrothorn, you will be crippling them with sleep. Sleep will provide amazing support to your relatively frail team, granting your Rain Sweepers free switch-ins.
If you're putting any Grass move for Gastrodon, it should be on Starmie. You honestly don't want your choice mons to be locked into a grass move, the ultimate chance for being set-up bait. Starmie is naturally a great lure to Gastrodon, so it would have no problems 2-shotting it. It can then proceed to sweep a little on its own as well. I recommend Grass Knot > HP Grass, since Starmie's primary goal is to Spin away hazards, and HP Grass would do shit to Jellicent. Give Starmie Expert Belt to give it the 20% oomph it needs to break through Jelly and Gastri. Jolteon and Starmie can be belt friends. Grass Knot replaces Tbolt (why no Thunder).
Wouldn't Baton Pass be more fitting than Volt Switch? It lets Jolteon escape from Dugtrio and Pursuit Ttars, and lets it pass its Substitute. Unless you use Substitute very sparingly, only for emergency situations. It's something to consider imo.
Not having anything on Dugtrio to hit Flying / Levitator Pokemon is sort of scary, imo, since so many mons can set up on it. Stone Edge / Rock Slide / Rock Tomb should go over Sub imo... What does Sub do other than ensure max-damage Reversal? Is Max-damage Reversal necessary to take out Ttar? Sorry if this is a stupid question... haven't used Dugtrio myself.
Thanks for sharing your love.