Hey, nice sun team.
You're team is quite weak to one of the most common sun counters: Latias. Everything on your team is OHKO'd after Stealth Rocks by Draco Meteor. In the same way you're team is rather weak to physical DD users like Dragonite and Salamence. Even though Landorus-T has intimadte and a lot of bulk, it still doesn't like taking Outrages / Dragon Claws. I'd suggest changing Victini -> Scarf Jirachi
and changing Hidden Power [Fire] -> Hidden Power [Ice]
on Venusaur. This way you can revenge kill Outrage locked dragons with Ice Punch and have something that can take a Draco Meteor to an extent. Jirachi does scouting and Tricking just as well as Victini, but does better vs dragons. Iron Head is great for flinches and STAB. Jirachi also gives you a switch in to Tornadus-T, which can just Hurricane away on your team as it is now, and KO it with Ice Punch. I don't think you need HP Fire as much on Venusaur as Scizor isn't much of a problem. Being able to revenge kill dragons like Garchomp and Salamence, which Jirachi can not always outspeed at +1, looks like something your team could use better.
Secondly I noticed that your sweepers are both special attackers. Your team has a tough time handling Chansey / Blissey so I'd recommend running Swords Dance -> U-turn on Landorus-T
. The best you can do at the moment is Trick it and if that fails all you can do is Earthquake with Landorus-T which Chansey can just Wish / Softboil away. With Swords Dance you can do damage to Chansey to an extent that it can't Softboil stall you anymore (64% - 75%), making it easier to deal with the pink blobs and to sweep with Venusaur / Volcarona.
Now for some smaller things, don't run Thunder on Starmie. Change it to Thunderbolt
. Thunder has decreased accuracy in sun so it's really unreliable. Thunderbolt allows you to have a solid way of dealing with Gyarados outside of rain. For the second move slot, you might be better of running Recover
. Your team really doesn't have any trouble with Scizor and with Jirachi and Venu's HP Ice you don't really need Ice Beam as much anymore either. Being able to spin is really important since you carry an offensive Volcarona so I think making Starmie more durable is more important than either of those moves. The move set you run now is quite defensive so you can make the ev spread more defensive but it's up to you if you think wether that's necessary or not.
On Ninetales, I don't think you need Substitute that much. All it really does on that set is make predicting easier. You can't really stall something out with it in combination with WoW since it's damage is constant. Running Solarbeam
looks like a better idea. Since you carry Sunny Day you can use that on the obvious Politoed switch in and proceed to Solarbeam it making winning the weather war easier.
Hope I helped. Good luck !