First of all, it takes 4 EVs to make a new stat point, so giving a pokemon 255 EVs in one stat means wasting EVs.
Groudon alone makes this team an uber team, and an "1 uber metagame" doesn't exist. This team will have problems against other uber teams, and in OU, people will ***** about Groudon.
Quiet Exeggutor is lol, so is using Sunny Day on it when you already have Groudon anyway. Use Mild, Explosion/Hp Ice/Solarbeam/Sleep
[email protected] berry, Mild nature, and 140 Atk / 212 Spd / rest in SAtk.
Reversalken sucks, but I guess it could work to an extent. :/
Ampharos's EVs make me a sad panda. Use nearly max hp, some Atk, rest in SAtk, with Quiet nature.
That Metagross is NOT standard, and it should never have a -def nature. Use Brave, and less Atk.
DDgyara doesn't work anymore imo, with Zapdos being on 99.99% of the OU teams, but meh.
Well, I hope this helps.
__________________
I'm not an elitist, I'm just better than all of you.