Personally, I love weather teams, so I decided to rate your team!
Synergy / Typing
Your team has quite a few weaknesses: 2x Rock , 2x Ghost , 2x Grass, 8x Electric , 2x Dark.
Obviously, your major weakness is Electric, so I'll try to improve on it.
Even though Rain teams are sorta a thing of the past, Rain Offense is still viable in many tiers.
Movesets / Pokemon
Here I'll be replacing and fixing some of the Pokemon's movesets.
Politoed
This set is okay, but you should use Politoed's support moves.
Sample Moveset of Support Politoed:
Ability - Drizzle
Item - Damp Rock
EVs - 248 HP / 164 Sp. Def / 96 Speed
Moveset:
-Scald
-Hypnosis / Toxic
-Encore
-Rest
The EVs are meant to outspeed max Speed Azumarill and deal with threats like Charizard Y.
Scald is STAB and chance of burn. Hypnosis puts the opponent to sleep, but has a low accuracy. Toxic has better accuracy and deals damage that builds up each turn. Toxic can also catch threats like Latios/Latias on the switch-in. Encore is used to trap set-up Pokemon. For example, use it when you're expecting Azumarill to use Belly Drum.
Omastar
I gave advice about Omastar in the comments, but if you need details on the set for Kingdra, here it is:
Kingdra@Life Orb
Ability: Swift Swim
EVs: 252 Sp. Atk / 216 Speed / 46 HP
Modest Nature
Moveset:
- Ice Beam / Rain Dance
- Hydro Pump
- Draco Meteor
- Dragon Pulse / Ice Beam
Obviously, do not have Ice Beam on the same set. So Ice Beam is coverage, Hydro Pump is powerful STAB, STAB Draco Meteor can land easy kills on other Dragon-types, and Rain Dance is just in case if you need it.
Kabutops
Kabutops sorta gets outclassed by M-Swampert as a rain sweeper and, since you're thinking about replacing M-Scizor with Ferrothorn, your mega slot is free.
So why not? Anyways here is the set:
Swampert@Swampertite
Ability: Damp -----> Swift Swim
EVs: 252 Atk / 252 Speed / 4 Def
Adamant / Jolly Nature
Moveset:
- Protect / Power-up Punch / Superpower
- Ice Punch
- Earthquake
- Waterfall
Protect allows a free turn to Mega Evolve (without getting attacked). Power-up Punch is generally used for boosting attack, while Superpower gives immediate power. Ice Punch is coverage against Grass-types (like M-Sceptile). Earthquake and Waterfall are dual STABs.
Tornadus-Therian
Pretty good set, but I may know the problem for this Pokemon.
On your team, Tornadus-Therian is supposed to act like a pivot.
You can't really do that with Choice Specs, so switch it to something like Life Orb.
Also replace Superpower with Focus Blast (even though it has lower accuracy, it better abuses its Sp. Atk and can mean the difference between an OHKO or a 2HKO).
Finally, replace Sludge Bomb with Taunt or Knock Off. Sludge Bomb doesn't give much coverage, but Taunt prevents the opponent from using set-up moves or entry hazards. and Knock Off is useful in getting rid of the opponent's items.
Latias
Your EVs on Latias are a bit weird. You should invest more in HP and Sp. Atk. It should be like 72 HP / 184 Sp. Atk / 252 Sp. Def. And the nature should either be Modest or Timid.
To be honest, Defog > Rain Dance and Psyshock > Energy Ball. Defog is good for removing hazards and Psyshock forms Dual STAB with Draco Meteor. You don't really need 2 rain inducers; Politoed is a pretty reliable rain setter and if you play Politoed right, you can have him induce 24 turns of rain. Energy Ball doesn't really give much coverage either because you're replacing M-Scizor with Ferrothorn.
M-Scizor
I already suggested replacing M-Scizor with Ferrothorn, but I'll give you a good set for Ferrothorn.
Ferrothorn@Leftovers
Ability: Iron Barbs
EVs: 252 HP / 88 Def / 188 Sp. Def
Relaxed Nature
Moveset:
- Stealth Rock / Spikes
- Leech Seed
- Gyro Ball / Power Whip
- Power Whip / Thunder Wave
Ferrothorn can set up Stealth Rock / Spikes and Leech Seed pretty well because its overall bulk. Gyro Ball and Power Whip are both powerful STABS. Thunder Wave cripples most sweepers.
I put the suggested moves in italics. Note that these are mere suggestions and that you can tweak the moves if you feel something works better.
Overall Rating
Your team is good, but it has some notable flaws that you can fix by simply updating the movesets or replacing the Pokemon.
If you have any questions, just ask it in the comments.
Hope I helped!