Firstly why the lack of items?
I also suggest that you change your natures to + Speed -Useless stat you don't need. I found that change to be invaluable in my battles. (Only on your primary sweepers though)

Gengar. I dislike Focus Blast, Hypnosis, and any move with less than 80% Accuracy. Might I suggest swapping those two moves out with Sludge Ball, Thunderbolt, and or Energy Ball?

This Starmie isn't standard but that's not a bad thing. You may or may not regret leaving out Rapid Spin.

You might as well trade off Hydreigon with Salamence with that moveset. Hydreigon is better suited to be a special sweeper. I would suggest Tri-Attack, Dragon Pulse (Or Draco Meteor), Dark Pulse, Earth Power, Flamethrower, Surf, Hidden Power, Flash Cannon. You have many combinations to choose from.

Blaziken. You should either change the ability to Speed Boost or get a Ninjask instead. Ninjask--> Swords Dance and Baton Pass and two of the following: Substitute, Protect, Bug Bite.

I suppose that your Blissey is alright.

Blastoise has a decent moveset though I don't see the point of having Flash Cannon on it as opposed to Ice Beam. I'm also a bit iffy on Seismic Toss but I've never seen an SToss Blastoise either.

 

Don't feel like doing the rest tight now.

 

Gengar - Psychic is a useless coverage move. Replace with T-Bolt and give it a Life Orb or something.
Starmie - That thing needs Choice Specs if you want it to be a Special Sweeper. Otherwise, give it a Life Orb and replace Rain Dance with Rapid Spin, and Thunder with Thunderbolt, and change the ability to Natural Cure.
Hydreigon - Quite unfitting for the set. You could either make it a physical sweeper instead, or replace it with Garchomp or Haxorus. (or if you'd like, maybe even Dragonite or Salamence)
Blaziken - There's no point in using Blaze, replace it with Speed Boost, and turn it into whatever you like, be it a wallbreaker (a mixed attacker) or a physical sweeper with Swords Dance.
Blissey - Softboiled and Wish > Heal Pulse. Aromatherapy is redundant, take it out, (except if you want to be a cleric, then take out Wish and leave Aromatherapy). Counter could be good, if used properly, however I prefer Seismic Toss or Flamethrower to it. Keep Toxic.
Blastoise - Seismic Toss? Rain Dance? FLASH CANNON? Scrap the whole set please.

You've gotta be shittin me. Earthquake? On a Blissey? And take off TOXIC?

[sarcasm]We might as well add a Choice Band and turn it into a Physical Sweeper.[/sarcasm]

 

Fixed your Fix lol