Hey bro, this is a pretty nice team. At a first glance, I think the biggest threat is easily sub dd gyarados. Like most drizzle teams, sub gyarados can pose a massive threat if you happen to have a few places where it can set up on. Although jolteon outruns most gyarados variants after one dragon dance, I really don't think that this is enough. If you happen to break gyarados' sub one time with volt switch, it can easily sub down again as you go into another team member meaning that that it can get a second dd and sweep your team easily. On the other hand, if jolteon uses thunder, then gyarados can easily waterfall jolteon for an easy ko (or sub down again and actually dd again). Either way, jolteon is not one to rely on for beating sub dd gyarados alone. To be honest with you, I think that if you perhaps tried a rotom-w on this team again, gyarados won't be as much of a problem. I mean, jolteon doesn't exactly switch into tornadus-t any better than rotom-w can, so you might as well use rotom-w which can switch into stuff like mamoswine, gyarados, tornadus-t etc easier. I think running a choice scarf set would actually be quite interesting. This team definitely has an offensive sort of playstyle, and timid or modest choice scarf hydro pump hits like a truck, meaning that between rotom-w / starmie / dragonite, you should have no trouble breaking down and cleaning up most types of teams.
If you decide to test rotom, I'd probably run hpump / volt switch / hp ice / thunder. Trick is an option I suppose over thunder, but I think that putting massive pressure on stuff like gyarados is much more valuable than possible tricking chansey / blissey a choice scarf. If you really don't think that rotom-w does the job against gyarados and tornadus-t, then you could easily try out another steel type on this team. Outside of jolteon, you lack a pretty crucial flying resistance and jolteon is definitely not the most reliable of switches into tornadus. I think something like sub + calm mind jirachi would work excellently over toxicroak. Although toxicroak work well against ferrothorn, I think that something like sub calm mind jirachi would work excellently as a cleaner on this team. Jirachi sets up against non bulldoze ferrothorn and can get to +6 easily enough if ferrothorn decides to stay in. Not to mention that jirachi is a solid flying resist and also matches up well against other drizzle teams as well as stall teams. I'd try a set with substitute / calm mind / psyshock / water pulse, timid nature, max speed and hp as that combination of moves easily beats gastrodon as well as calm mind reuniclus (which is pretty annoying to this team).
As for some small changes, I'd run stealth rock on ferrothorn. Offensive teams such as this absolutely need stealth rock. Although spikes is pretty nice to have, stealth rock is beneficial for your drizzle abusers to hit hard with. Perish song on politoed is also a very good option here. Hypnosis, although pretty good, is extremely unreliable. Perish song gives you a safety net as a last ditch effort versus stuff like sub calm mind jirachi, dragonite, gyarados, volcarona etc. gl!