Ok, I'm not exactly a veteran at VGC15 (pretty new myself actually), but I'll try my best at this.
First off well, your team does not actually fit in well as a VGC team. There are some things present in your team right now that are outright non-viable in the metagame. Don't mind my saying this, but Dusknoir and Forretress are simply bad choices. Dusknoir is bad because it's almost completely outclassed by Dusclops and Cofagrigus, which aren't really viable either. Forretress is bad because hazards do next to no work in doubles, mostly due to the much faster pace (meaning switches occurring very rarely) and that the damage dealt is almost negligible in most cases.
But hey, it's not all bad. Let's go through all your pokemon and try to correct what we can.
Charizard:
Oh by the way Charizard Y is much better in doubles than X, because Drought's 5 turns make a huge difference here. But it's vulnerable on the turns it Mega evolves and other moments when both of your opponent's pokemon gang up on it. So, as for the first correction, give it Protect.
Protect is phenomenal is VGC, as it guards one of your pokemon and allows the other to feel free to spam an attack. You can replace Air Slash for it (you don't lose much coverage anyways).
Secondly, the EVs are a little off. If you really want to keep it simple, go for more speed investments and reduce all that Special Defense (speed is more crucial than special defense) and give it a Timid nature. This way you can outspeed or speed-tie with most base speed 100 pokemon.
Right, so your team has a weather inducer (a pokemon that alters the weather). Why not take advantage of it? You might as well, because the extra muscle can make all the difference.
Jolteon:
The problem with sparky here are it's moveset and item, which will have to be revamped top down. Magnet Rise is a gimmick at most and between Shadow Ball and Signal Beam you don't cover much. Focus Sash can be rendered useless due to Hail, Sandstorm and double attacks. Here's a set people use:
Jolteon @ Choice Specs
Ability: Volt Absorb
EVs: 252 SpA / 252 Spe / 4 HP
Timid Nature
- Thunderbolt
- HP Ice
- Shadow Ball
- Hyper Voice
This set offers Jolteon awe-inspiring offense with Specs, and it's already fantastic speed makes it a terrifying pokemon to face. It utilizes a pseudo BoltBeam, which is basically Thunderbolt and Ice Beam (in this case HP Ice, hence pseudo). It covers a huge chunk of the current metagame. The last two slots are, in all honesty fillers.
It also offers great synergy with MegaZard Y, as Jolteon can eat up any electric attacks thrown at it and strike pesky water types very hard.
Machamp:
The only reason Machamp is not included in the non-viable list is because it provides great utility with Wide Guard and Quick Guard. But giving it an Assualt Vest renders it incapable of using either and practically making it a sitting duck. So it might be a good idea to scrap Assault Vest for Leftovers (recovery) and throw in Wide Guard.
The reason as to why Wide Guard is because MegaZard Y is weak to Rock Slide, Jolteon and Aegislash (an addition I'll explain briefly) are weak to Earthquake. All of these are common spread moves, which Wide Guard can completely route.
Also, run Rock Slide over Stone Edge and if you want to, replace Poison Jab with Quick Guard.
You could also consider a more defensive set on this one.
Garchomp:
This pokemon is mostly fine, except that you should run Rough Skin over Sand Veil and Adamant over Naive nature. Also, consider running Protect over Fire Fang as it's a lot more useful.
Right, with this I conclude the pokemon that I found to look good on this team. As mentioned earlier though, two of your pokemon had to replaced for better fits. Here they are:
Venusaur @ Life Orb
Ability: Chlorophyll
EVs: 180 HP / 252 SpA / 76 Spe
Modest Nature
- Sludge Bomb
- Giga Drain
- Sleep Powder
- Protect
Aegislash @ Weakness Policy
EVs: 252 HP / 4 Atk / 252 SpA
Quiet Nature
- King's Shield
- Shadow Ball
- Flash Cannon
- Shadow Sneak
OR
Bisharp @ Life Orb
Ability: Defiant
EVs: 4 HP / 252 Atk / 252 Spe
Adamant Nature
- Knock Off
- Sucker Punch
- Iron Head
- Protect
Venusaur and the sun goes a long way back. Now with MegaZard Y readily supplying sun, you could opt to run the famous ChloroSaur set on Venusaur, which is basically an offensive Chlorophyll Venusaur. This leafy dino is probably the fastest thing under the sun (hehehe wordplay) which allows it to attack or put foes to sleep eith Sleep Powder much before anything reacts. It complements your team well, so here it is.
Aegislash is mainly the defensive part of your team, and your Trick Room counter. It balances out your Ice and Flying weakness, while taking hits like a champ. Weakness Policy is a force that can change the tide of a game in a matter of seconds, and it's fearful when used right.
Bisharp on the other hand, is a hard counter to Intimidate (which gained popularity with Landorus-Therian back) and also counters Trick Room. Personally I think Bisharp is the better option, but the choice is yours.
That is all! Hope you enjoyed reading that extra long wall of text, an more importantly hope it helped in any matter :)
