Well,i dont know what to say,but seriously your team needs a lot of improvement.
Arceus-Steel:
Good.So,I am not gonna talk about it since you like it.
Landorus-T:
What? Ice gem? No,landorus has a monstrous attack and dont go for a SpA.Replace HP-ice for Outrage and replace ice gem for Life orb.Then it will be a monstrous attacker.
Palkia:
Yeah,your palkia is awesome! Only one suggestion,just replace that Lum berry for Choice scarf for more power.
Deoxys-S:
Your moveset really needs a lot of imrovement,Try this set:
Deoxys-S@Lum berry
EV's:4 Def / 252 SpA / 252 Spe
Nature:Timid
Ability:Pressure
Stealth rock
Spikes
Psychic
Ice beam
One look at its ridiculous Speed and reasonable bulk should sufficiently explain why Deoxys-S is such a hot commodity for its ability to lay down entry hazards both quickly and reliably. On top of this, Deoxys-S has many moves at its disposal to check opposing leads, such as stealth rock to screw the likes of Volcarona,spikes to damage the for,Psychic as stab and ice beam to screw those Dragons.
Manaphy:
Manaphy definitely needs some rain support MF.It needs a lot of improvement.Try this:
Manaphy@Leftovers
EV's:252 Hp/252 Spe/4 SpA
Nature:Timid
Ability:Hydration
Rain dance
Calm mind
Rest
Scald
While Manaphy's other setup move, Tail Glow, seems more appealing with its massive +3 Special Attack boost, Calm Mind is actually Manaphy's most reliable form of stat boosting. A common way of defeating the Tail Glow set involves equipping Kyogre, Palkia, or Dialga with a Choice Scarf and taking it down with Thunder. However, with a Calm Mind boost, the aforementioned Pokemon will not be doing enough damage to stop Manaphy from setting up another Calm Mind, using Rest to recover the damage, and then waking up immediately if rain is active. Manaphy can then alternate between Calm Mind and Rest to slowly set up until it is ready to sweep. The beauty of this set is Manaphy's ability to singlehandedly destroy stall teams without crumbling immediately to offensively based teams. While the Tail Glow set is scary due to its ability to hit extremely hard and quickly, the Calm Mind set instills a whole new type of fear, a fear that is slowly sewn into your opponent's mind as they helplessly watch the prince of the seas take apart their team. Calm Mind and Rest are obviously the crux of the set, allowing Manaphy to set up on what would have been 2HKOs. Scald is the preferred STAB in this case, as a potential burn can cripple the physical attackers attempting to bypass Manaphy's Special Defense boosts.
Credit to smogan for this one.
Darkrai:
Have focus sash for darkrai,It can be taken out easily by the likes of mewtwo using aura sphere.Replace thunder with ice beam for more coverage.
Thats it!