Excadrill
The Item for your Excadrill should be life orb, as it should be there to do as much damage as possible before fainting. Your ability should be Mold Breaker, as you should not run Sandstorm; your Pokemon will be murdered first turn, and setting up is just simply not an option. Replace X-Scissor with Rock Tomb; it will help against bulky flying types. I would also suggest using an adamant nature.
Metagross
Decent moveset, just replace Explosion with Stealth Rock, and change your Assault Vest to Life Orb. This will improve its usability by letting it set up as well as attack.
Steelix
Why. Do. You. Waste. Mega-Stone. On. Steelix.
Replace Steelix with Mega-Scizor, with the following moveset. Win rate will go up immediately.
Scizor @ Scizorite
Ability: Light Metal
EVs: 248 HP / 16 Atk / 60 Def / 124 SpD / 60 Spe
Adamant Nature
- Swords Dance
- Roost
- Bullet Punch
- Bug Bite
Magnezone
Lock-on Zap cannon, like the Excadrill thing, is way too slow.
They will OHKO you when you lock-on, or they will outspeed you the next turn and KO you.
Run a completely different set with better coverage, and more reliable moves.
Magnezone @ Choice Scarf
Ability: Magnet Pull
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Volt Switch
- Hidden Power Fire
- Flash Cannon
- Thunderbolt
Probopass
Again, I am not sure why this is here, but it can work.
The set is weak and unreliable, and your zap cannons just do not work, so I will give you a new set to work with.
Probopass @ Leftovers
Ability: Magnet Pull
EVs: 172 HP / 252 SpA / 84 Spe
Modest Nature
- Volt Switch
- Flash Cannon
- Earth Power
- Stealth Rock
Durant
Replace Durant with Skarmory, which has much better utility and usability, as well as viability.
Skarmory @ Leftovers
Ability: Sturdy
EVs: 252 HP / 4 Def / 252 SpD
Careful Nature
- Iron Head
- Spikes
- Roost
- Whirlwind
Conclusion
Your team is good in general, but some of the changes are necessary; you do not have to listen to me, but just wondering -- is this in the actual game or in Pokemon Showdown?
Let me know.