Sigh. I don't know why I'm even bothering, especially with a team like this, I don't post very often here anymore. But eh. To put it bluntly... its not good... really. I don't know if this is just for in-game or with friends or competitive or whatever. >> So I'll just give you the basic stuff here.
One big issue with your team is well... Venusaur for example. It has FOUR Grass-type moves, and that's bad. Why have four of the same type of move?
Also, I'll be giving out natures, though I'm not sure if you're willing to re-breed, especially that Pidgeot.
Dragonair
~Adamant
-Dragon Rush/Outrage
-Iron Tail
-Dragon Dance
-Return/Waterfall/Aqua Tail/Protect
Dragonair has better Attack than Special Attack, so all these moves are physical. You don't have much of a choice for the STAB Dragon-type move. Dragon Rush has low accuracy and Outrage lasts for 2-3 turns and leaves you confused. Your choice.
Iron Tail also lacks in accuracy but its your only defense against Ice-types.
Dragonair's attacking power isn't the best, and its Speed is even worse, so Dragon Dance will help.
The last move it just a filler, choose what you feel would be useful.
Pidgeot
~Adamant/Jolly
-Aerial Ace/Brave Bird
-Return
-Steel Wing
-U-Turn/Agility/Quick Attack
Aerial Ace has the same attack power as Wing Attack but it never misses... so why have both when Aerial Ace is better? Brave Bird is only received through breeding, and yeah, since that thing is shiny, I doubt you'll be training another.
Return makes for a nice move and it gets a boost in power from STAB.
Steel Wing is so you're not totally helpless against Rock and Ice-types.
Last move again is a filler, U-Turn makes a powerful hit and run type move, especially if used against an unsuspecting Psychic-type. Pidgeot is already kinda speedy, but Agility can make it better so it can keep up with other things. Quick Attack makes a nice move, coupled with that fact that Pidgeot has high Attack and it gets a STAB boost, it would prove handy if you need to hit first. Note that this could also go in place of Return.
Ninetails
~Modest/Timid
-Flamethrower
-Dark Pulse/Confuse Ray
-Extra Sensory/Sunny Day
-Energy Ball/Solar Beam
Flamethrower is, obviously, for STAB, and about the best move you're gonna get, Fire Blast has ugly accuracy and low PP, and Overheat lowers your Special Attack which is already kinda low.
Dark Pulse would give you some coverage against Psychic and Ghost-types. Confuse Ray is always handy though, and has the potential to turn any fight in your favor. Your choice.
Extra Sensory is also for coverage, plus its a decent move. In order to get Extrasensory you have to hold back evolving Vulpix until its level 44. Or you could give it Sunny Day and then Solar Beam as the last move, but I'm afraid Ninetails doesn't have the Defense to set it up, so you'll have to take care if you decide to go that route. Solar Beam would be your only defense against your three weaknesses; Water, Ground, and Rock.
OR, you could give it some effort and breed Energy Ball onto it. Unfortunately, this can only happen via Smeargle and its Sketch. Very worth it though in my opinion, and that means you're not have to waste a move slot for Sunny Day.
Venusaur
~Hardy/Docile/Serious/Bashful/Quirky
-Energy Ball/Giga Drain
-Sludge Bomb/Toxic
-Synthesis/Leech Seed
-Earthquake
The Grass-move is your choice, either is good. Just remember that though Energy Ball is stronger, Giga Drain can help gain some badly needed health in a pinch.
Sludge Bomb is also another STAB move and a powerful Posion-type move, although its not particularly effective against anything other than another Grass-type, it'll deal nice damage to anything not resistant to it and may poison them. There's also Toxic is you just want to go with that...
Synthesis is also helpful for regaining HP, but I prefer Leech Seed, since it steals from the opponents HP and is a constant source of minor healing.
Earthquake is a powerful move and will help against your Fire weakness, its also just an all around good move and a good idea to have on any team.
Milotic
~Bold/Modest/Calm/Timid
-Water Pulse/Surf
-Ice Beam
-Dragon Pulse
-Recover/Aqua Ring
I'm not a fan of Milotic's myself, but I cannot deny their potency. Water Pulse or Surf, either is good. Just remember that while Surf is stronger, it also hits your partner in double battles. Water Pulse still has decent strenght and it can confuse the enemy.
Ice Beam is for defense against Grass and is there for that fact the you lack an Ice-move.
Dragon Pulse is just an overall good move to have, and will prove useful against Dragon-types along with Ice Beam.
One of these two healing moves is a good idea to have, simply because I recommend giving your Milotic the Flame Orb item. "What? Why would I give my Milotic an item that gives it a burn status?" Well, its simple really. Milotic's ability raises its Defense by a significant amount when under a status effect. The side effect is the burns cause damage, so a simple Recover would take care of that. Even if you don't choose to have Flame Orb on it, a healing move is still a good idea.
Blissey
~Bold
-Seismic Toss/Counter
-Softboiled
-Ice Beam
-Aromatherapy/Thunder Wave/Attract
It seems Blissey can't learn Seismic Toss in 4th gen, which means you'd have to migrate it from FR/LG if you want that move. If that's not possible then you could breed for Counter.
Softboiled is obviously for heal purposes.
Ice Beam is just a flat-out good move for Blissey, especially with its Serene Grace ability, higher chance of freezing.
Your choice here, any move would prove useful. Aromatherapy also takes some breeding though, so you might find yourself hard at work.
So yeah, that's about it...