This team feels like it needs some work. First off, a lot of these Pokemon are unviable in OU. I will be going over replacements and/or changes.
Togekiss
In OU, Togekiss is usually used as a Nasty Plot sweeper or support. First off, Pixie Plate is bad, especially since Heavy-Duty Boots exist and are almost always run on Togekiss. Another possible set would be:
Togekiss @ Heavy-Duty Boots
Ability: Serene Grace
EVs: 252 HP / 120 Def / 136 Spe
Timid Nature
- Roost
- Defog / Nasty Plot / Thunder Wave
- Air Slash
- Heal Bell / Flamethrower / Aura Sphere
Vileplume
Vileplume is completely outclassed in OU as an offensive grass type by Kartana and Rillaboom, whereas defensively Ferrothorn would be a better choice. I'll provide sets for all three, but I think Kartana and Rillaboom are better choices for this team.
Rillaboom @ Choice Band / Life Orb
Ability: Grassy Surge
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant / Jolly Nature
- Grassy Glide
- Swords Dance (if Life Orb) / Wood Hammer
- Superpower / Drain Punch / U-Turn
- U-Turn / Knock Off
Kartana @ Choice Scarf
Ability: Beast Boost
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Leaf Blade
- Sacred Sword
- Knock Off
- Smart Strike / Defog
Ferrothorn @ Leftovers
Ability: Iron Barbs
EVs: 252 HP / 4 Def / 252 SpD
- Leech Seed
- Spikes / Stealth Rock
- Knock Off
- Power Whip / Protect
Magnezone
Now, if you're going to use Kartana or Rillaboom, Magnezone has amazing synergy with them due to Magnet Pull trapping their major answers, the metal birds (Corviknight / Skarmory). It can also deal with Ferrothorn using a Sub + Body Press set. I'll provide sets for both Specs and Sub + BP
Magnezone @ Leftovers / Air Balloon
Ability: Magnet Pull
EVs: 252 Def / 116 SpA / 140 Spe
Modest Nature
- Iron Defense
- Substitute
- Body Press
- Thunderbolt
Magnezone @ Choice Specs
Ability: Magnet Pull
EVs: 4 Def / 252 SpA / 252 Spe
Modest Nature
- Thunderbolt
- Volt Switch
- Flash Cannon
- Steel Beam / Toxic / Body Press
Alakazam
Alakazam seems to have a lot of threats that can easily kill it that the rest of the team is also fairly weak to, like Zeraora and Dragapult. I think you should instead use Latios, another bulkier Psychic type that can deal with both aforementioned Pokemon with its Scarf set after some chip.
Latios @ Choice Scarf
Ability: Levitate
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Draco Meteor
- Psychic / Psyshock
- Trick
- Mystical Fire / Aura Sphere
Milotic
Milotic is outclassed entirely as a bulky water type by Toxapex, with its has huge bulk combined with Regenerator, Recover, and Haze that makes killing it extremely frustrating. It can be a great physical wall with Rocky Helmet, or it can run a Specially Defensive set.
Toxapex @ Rocky Helmet / Black Sludge
Ability: Regenerator
EVs: 252 HP / 252 Def / 4 SpD OR 252 HP / 4 Def / 252 SpD
Bold / Impish / Relaxed Nature
- Scald / Knock Off
- Recover
- Haze
- Knock Off / Scald / Toxic / Toxic Spikes
Lucario
As a Fighting-Steel type Lucario is completely outclassed by Zamazenta-Crowned in the current metagame, with far superior stats both defensively and offensively. It does work best with Wish support, but if Rillaboom is on the team the grassy terrain can be very helpful for recovery.
Zamazenta-Crowned @ Rusted Shield
Ability: Dauntless Shield
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant / Jolly Nature
- Howl
- Close Combat
- Behemoth Bash
- Wild Charge / Ice Fang
Those are all my thoughts on the team; hopefully I was able to improve it.