Okay here's a quick rate and mess around with your team. I wanted to give you a weather but the problem was, half your team doesn't function under one but functions under another etc. and vice versa. So I changed alot. Also remember this rate is off the spot I havn't tried much yet and didn't pay alot of attention to the synergy. Note also, you can make a rain team out of your current team, and with my rate if you want replace one of the pokemon with Victini in order to keep more pokemon from your original team. I havn't tested the below team or anything so it might be horrible. XD. You can run a weatherless team if you want as well, so if you want i'll write up another one which just fixes up your current pokemon movesets and doesn't change em,
Ninetales @ Air Balloon
EVs: 252 SpA / 4 SpD / 252 Spe
Trait: Drought
Timid Nature
~ Sunny Day
~ SolarBeam
~ Fire Blast
~ Nasty Plot
Standard offensive Ninetales. Sunny Day stlil lets you change the weather if you want, while Solarbeam/Fire Blast give good coverage and power in the sun. Nasty Plot is to boost Ninetale's lackluster attack. Air Balloon is a trolly item and actually works... when the opponent forgets to read the screen. Which happens more than you think and can be a gamechanger :P
Donphan @ Leftovers
Trait: Sturdy
EVs: 252 HP / 252 Def / 4 Spe
Impish Nature
~ Rapid Spin
~ Earthquake
~ Stealth Rock
~ Ice Shard
Fire Types all hate hazards, so rapid spin support is much appreciated. Earthquake gives Donphan STAB while Ice Shard can revenge kill. Stealth Rocks allows Donphan to get it's own hazards up.
Blissey @ Leftovers
Trait: Natural Cure
EVs: 4 HP / 252 Def / 252 SpD
Calm Nature
~ Wish
~ Protect
~ Seismic Toss/Ice Beam/Flamethrower
~ Toxic
Blissey passes Gargantuan wishes around your team, giving them new life :D. Toxic for some status, protect allows to stall more and Seismic Toss/Ice Beam provides an attack. Seismic toss is more reliable, but Ice Beam can beat dragon types which Flamethrower gets Pseudo-STAB.
Dugtrio @ Focus Sash
Trait: Arena Trap
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
~ Reversal
~ Earthquake
~ Stone Edge
~ Memento
Dugtrio with Arena Trap is a boon for Sun teams. It beats T-tar with Reversal after getting pushed down to focus sash, and can take out weakened politoeds (and opposing ninetales). It also takes out two massive threats in Heatran and Tentacruel.Memento is used over Stealth Rock since you already have that on Donphan, and since Dugtrio is on 1hp when you use it, wynaut give one of your other pokemon a free setup turn?
Venusaur @ Life Orb/Black Sludge
Trait: Chlorophyll
IVs: 2 Atk / 30 SpA / 30 Spe
EVs: 72 HP / 4 Def / 252 SpA / 180 Spe
Timid Nature
~ Growth
~ Giga Drain
~ Hidden Power Fire
~ Sludge Bomb
More standard fare Venusaur sweeper. Provides a nice resist against Water (not that you really need it) and is nuetral against Ground which is always nice. Growth sets up (+2) in sun, Chlorophyll doubles speed, etc. etc. Giga Drain provides healing, Hidden Power gets Pseudo-STAB in sun and Sludge Bomb rounds off the set. Remember Heatran walls the living daylights out of this so try getting Dugtrio or Donphan to beat it beforehand if you see one. A memento from Dugtrio then switching into Venusaur is great, as it effectively means you get a free Growth up - which is easily a game changing situa
Garchomp @ Choice Scarf
Trait: Rough Skin
EVs: 4 HP / 252 Atk / 252 Spe
Naive Nature
~ Outrage
~ Earthquake
~ Fire Blast
~ Dual Chop
Scarf Garchomp. Fire Blast > Stone Edge since this a sun team and allows Garchomp to get around some of it's more usual counters (I'm looking at you skarmory). Dual Chop is in the last slot to break substitutes, with Earthquake/Outrage forming dual STAB attacks.