Happy New Year! I’ve got some suggestion for you :D
It will improve your team to do this:
1. It’s fine to run a modest nature on Charizard Y. 2HKO on Heatran is enough. you might rather want that longevity by not running a rash nature.
Relevant Calcs.
0 Atk Mega Charizard Y Earthquake vs. 0 HP / 0 Def Heatran: 284-336 (87.9 - 104%) -- 25% chance to OHKO
0 Atk Mega Charizard Y Earthquake vs. 252 HP / 0 Def Heatran: 284-336 (73.5 - 87%) -- guaranteed 2HKO after Leftovers recovery
2. Don’t use two megas on same team. It’ll become a liability. I suggest using Assault Vest on Metagross instead if you want to keep it.
3. Don’t use Jolteon. It’s outclassed, and ridiculously frail. It’s got speed, but that’s about it. Use something else like Raikou, which has got much more bulk and it can do the same thing as Jolteon can. If you want a revenge killer, use scarf Landorus-T. It outspeeds so many things.
4. Metagross: Splitting EVs is not a good idea. Putting the EVs in attack for Max attack is generally better.
5. Umbreon: Use Synchronize.
Inner focus just protects you from flinching, whereas umbreon can’t take care of fake out users: (M-lopunny and M-Medicham both have High Jump Kick which wrecks Umbreon, seeing you don’t have protect.)
Paraflinch users: Jiraichi (It gets wrecked by Zard Y) Togekiss (You can’t do anything to it with Foul Play, and it can heal bell off the toxic.)
Conclusion: Inner focus is kinda useless.
Suggested (not required to do good, but might help):
Garchomp:
You might wanna swap Stone Edge for something else. The only thing it hits is Fire-Flying Types in OU, and if you’ve got stealth rock up, talonflame and Charizards won’t switch in anyway.
Metagross:
It’s your own choice, but meteor mash is generally better.
Latias:
Psyshock allows you to hit specially defensive pokemon. It turns Latias into a mixed attacker, allowing u to deal with stuff like AV raikou and goodra.
Team problems:
You have some common weaknesses that you're not dealing with.
You have some pretty severe weaknesses to Ice and Ground
Example: Mamoswine with superpower/ Stone Edge practically OHKOs or 2HKOs everything on your team.
Something like a rotom-w might help you out. Ultimately, it's up to you what you want to do. :D Good luck!