I'll put all the changes I make in bold for you.
Shadow (Weavile) (M) @ Focus Sash
Ability: Pickpocket
EVs: 4 HP / 252 Atk / 252 Spe
Jolly Nature
- Fake Out
- Icicle Crash
- Knock Off
- Protect
You should use icicle crash instead of ice punch because it hits multiply targets and a chance for flinch. Also use protect instead of low kick since weavile is frail and needs it.
Magma (Heatran) (M) @ Leftovers
Ability: Flash Fire
EVs: 180 HP / 252 SpA / 76 Spe
Modest Nature
- Heat Wave
- Earth Power
- Substitute
- Protect
I wouldn't change anything here this is a pretty solid heatran.
Blue falcon (Latios) @ Life Orb
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
- Draco Meteor/Dragon Pulse
- Psyshock
- Protect
- Dragon Dance
I would go with dragon pulse instead of draco meteor because it has better accuracy, but you could go either way. I would go with protect over grass knot because Latios needs protect.
motoR-hsaW (Rotom-Wash) @ Lum Berry/Sitrus Berry
Ability: Levitate
EVs: 252 HP / 200 SpD / 56 Spe
Calm Nature
- Will-O-Wisp
- Protect
- Thunderbolt
- Hydro Pump
Rotom needs more SpD and needs some speed. Also expert belt is kind of usless, you need sitrus berry more to restore hp you loose or lum berry to heal status. Also protect goes well with him.
SirKight (Gallade) @ Galladite
Ability: Steadfast
EVs: 200 HP / 252 Atk / 56 Spe
Adamant Nature
- Protect
- Close Combat
- Zen Headbutt
- Ice Punch
M Gallade needs protect since he's frail. He also needs zen headbutt more than psycho cut since it can cause flinch. Ice punch is really just for coverage.
Togekiss @ Rocky Helmet
Ability: Serene Grace
EVs: 252 HP / 164 Def / 4 SpA / 28 SpD / 60 Spe
Bold Nature
- Follow Me
- Air Slash
- Thunder Wave/Roost
- Protect
I completely took out jirachi for two reasons. 1. It is banned from vgc and 2. It can only get follow me from an event in gen 5. I replaced it with togekiss because he is a really good follow me pokemon.
That's all I have to say about your team. Hope you like my advice!