Oh goody, Another team to rate!
Ferrothorn
Iron plate? That powers up Steel attacking moves by 1.2. The only steel move you have on this set is iron defense. Not an attacking move. Switch Iron plate to Rocky helmet to add damage from iron barbs. Iron defense is hard to set up because the opponent could easily switch into common fire types like Heatran and Talonflame. Swap that for stealth rock. Stealth rock alone takes half of talonflame's health! HALF!.. HALFFFFFFFFFF!!!!
Thunderus
You could run an different set with Choice specs, Thunderbolt instead of Thunder, and HP flying instead of rain dance. But your set is good anyway and you don't have to change it.
Mega Gardevoir
Substitute? Seems random. Swap for Thunder Wave (Cripples walls) or Will-O-Wisp (Cripples physical attackers)
Manaphy
Aqua ring + Hydration with rain dance is good. But to add to the Heals... Swap Mystic water for leftovers. Mystic water doesn't add much, and scald already has that good burn chance, plus, your only running one water attack. So there. Done that piece of cancer. (In a good way)
Talonflame
Ay! That's the same set I run with Talonflame! Only with Life Orb instead of leftovers... Leftovers? On a sweeper? kk. Swap 4 Life orb OR Sky/Flame plate
Snorlax
Noice.
(Remember, I AM BAD AT COMPETETIVE. (I don't care I spelt that wrong) So, you don't have to do whatever I say.