Greninja: Good, but Focus Sash is pretty bad on him. Give him Life Orb, I would say specs but you have spikes. Also, Scald>Hydro Pump.
Swampert: No real use for Rindo Berry. I would band him personally, but life orb would be good too. Great moveset though.
Gyarados: 2 turn move and no power herb. Ice fang is much better to cover grass. For the reason Scare-Wolf said, don't be too quick to mega-evo. You could still run mega if you wanted. Max out attack too. Expert belt is good if you decide to not to mega him.
Lanturn: Good set, but I'd run specs instead of lefties. You could also replace Dazzling Gleam with Volt Switch to make him a good scout.
Kingdra: Good set, but there is little point for rain dance. I'd run a sniper one holding a razor claw. Replace rain dance for dragon dance.
Clawitzer: I don't think you can get swift swim ones. Run mega launcher one with water pulse instead of scald. Use Choice specs for an item.
I think I need to mention Stall Ludicolo. He's hit neutral by Grass, and is really useful:
Ludicolo @ Leftovers
Nature: Can't remember what name, but it's +def/sp.def, -atk
EVs: 252 HP, 252 (sp.)def, 4 sp.atk
Ability: Rain Dish
Mega Drain
Scald
Rain Dance
Leech Seed
If you run the Ludicolo I suggested, don't change Kingdra. He would help him by setting up rain.