Hi, there are a lot of pokemons I love in this team. Especially Weavile who is terribly underrated, and Volcarona... because Volcarona is damn powerful.
First, I do not think Venusaur is a threat at all. Weavile deals with it, no matter what happens. Since your Ice Shard does over 80%, since he will use HP Fire and not Giga Drain (it doesn't kill you, in fact not even at +2), there is no reason to be afraid. You have a good chance to kill it with SR damage, a 100% chance to do so with Spikes and SR, and anyway LO recoil will eventually kill the Venusaur.
A Growth can be annoying, but you can bait the LO recoil with Forretress then revenge kill it swiftly anyway.
However, there are several weakness I can see.
Ganj4lf is very right when he talks about your Water resistances, you got Jellicent but the whole rest of your team gets totally annihilated by a Scarf Keldeo for instance. I know, Jellicent walls it, but Jellicent can do nothing, he can't set-up and pull off a sweep.
Thus, you need an offensive option to deal with Rains, because at the moment, Bulky Waters are your worst nightmare.
Here are my changes :
DD Dragonite > Donphan
Why, and what does it fix ?
Dragonite is usually a sample in any weatherless team for the resistances he brings against Rain and Sun teams. He's really hard to wall, people most of the time go for the revenge kill after baiting an Outrage. However with moves like Extreme Speed, after some DD it's really not so simple to kill this guy.
He will bring you what you need against Sun Teams, an extra priority move to deal with the Chlorophyl sweepers, and a resistance to both Fire and Grass moves. Keldeo being most of the time choiced, you can find many rooms to set-up. Politoed, Tentacruel etc, are all set-up fodders for your Dragonite considering the Lum Berry to clean a possible Burn or Toxic. You also win a stronger offensive presence in comparison to Donphan or Latias.
Donphan is out of place here in my opinion, his role collides with Forretress's one, and he can't really be an offensive threat. His niche is tiny, and he doesn't fit in many teams.
This change fixes many issues in one. But I see other minor changes that you could do to improve the team. here I go :
- Given the departure of Donphan I'd give Forretress SR.
It's usually not the best idea to put both SR and Spin on a single pokemon, but well, there is no other choice here. You don't need that much Spikes, else, shift your team for a Deoxys-D offensive team. But that's not the subject.
- Change Earthquake for GyroBall
What is the purpose of Earthquake here ? To me this move is here to catch Magnezone on the switch, or thanks to Sturdy. But you got Volt-Switch for that, no need to waste another move slot for a single pokemon. You are far less set-up bait, and you can hit Levitate pokemons like Latias or Gengar. Especially Gengar, since it's probably a pokemon who will like to switch on your Forretress, don't make his life easier (yes I know you can Volt-Switch with a good prediction and trap him with Weavile, but once Gengar manage to sub, all your checks become seriously shaky).
- Change Weavile to a LO set, put these 4 EVs in SpD
This is my personal choice, coming from my personal experience. Weavile doesn't like to be locked against a pokemon he can't hurt. Usually you prefer switch the moves with your amazing coverage. The Banded version doesn't land to many extra kills to worth the lost of the diversity. Weavile isn't a pokemon that love to switch in and out given the SR Weakness.
For the EVs, there is no reason to put them in Def, Weavile will die to any Physical attack, it's better to put it into SpD (his special bulk isn't that bad at all).
- Change Volcarona to a Lead set
With Dragonite, you become really weak to SR. But you got Forretress right ? I don't think it's enough. Volcarona performs really well as Lead, because you won't be killed by SR and random damage so easily.
I use myself this set on a team I made, this is really powerful and anti-metagame. This is the best offensive Deoxys-D counter (and reliable, since most of the usual Deoxys-D counter can be beaten by Magic Coat or.. Skill Swap/Pursuiter).
With this self-made set/EVs, you can outspeed Deoxys-D Timid version, and kill it with +1 Bug Buzz (they will probably Taunt you the first turn as you Quiver Dance). With Focus Sash and Giga Drain, you can pull off a sweep against a lot of classic Volcarona checks (like Terrakion scarf). Fire Blast is the Stab. This set is totally wrecked by Flying pokemons under Rain, but guess what ? you got a Weavile for this matter no ? :)
Moreover they need to put Politoed against you to activate the Hurricane spamming, if you don't fail the prediction game, you should be able to get out of here (don't show Giga Drain if you see that the Politoed is trying to kill you, and stack Quiver Dance! at +3 it's a 0HKO with Giga Drain, and Hurricane from Specs Tornadus-T does 65%, at +4 it does only 55 to Volcarona, while Giga Drain eats 50 % of Tornadus-T's life).
I did put the extra 80 EVs in SpD to maximize the recovery from Giga Drain and the boosts from Quiver Dance.
The sets :
...
Dragonite @ Lum Berry
4 HP / 252 Atk / 252 Spe
Adamant nature
- Dragon Dance
- Outrage
- Fire Punch
- Extreme Speed
Volcarona @ Focus Sash
252 SpA / 80 SpD / 176 Spe
Timid Nature
- Quiver Dance
- Giga Drain
- Bug Buzz
- Fire Blast
Good luck with your team, I hope I helped !
TL;DR