[RATE MY TEAM] Hey could someone help me with my team?

[AverageJoe]

Hey. I would really appreciate it if someone could help me with this team. I know the Gyrados set is pretty bad, but I did not think of a better replacement. I also have problems dealing with Toxapex, as Alakazam does not appreciate taking any hits and rotom is weak to water. Any help would be greatly appreciated. Thanks
-J

Alakazam-Mega @ Alakazite  
Ability: Magic Guard  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Hidden Power [Ice]  
- Psyshock  
- Energy Ball  
- Focus Blast  

Landorus-Therian @ Choice Scarf  
Ability: Intimidate  
EVs: 252 Atk / 4 SpD / 252 Spe  
Adamant Nature  
- Earthquake  
- U-turn  
- Stone Edge  
- Knock Off  

Rotom-Heat @ Leftovers  
Ability: Levitate  
EVs: 248 HP / 252 SpA / 8 SpD  
Modest Nature  
IVs: 0 Atk  
- Defog  
- Overheat  
- Volt Switch  
- Pain Split  

Celesteela @ Leftovers  
Ability: Beast Boost  
EVs: 252 HP / 4 Atk / 252 Def  
Relaxed Nature  
- Leech Seed  
- Protect  
- Heavy Slam  
- Flamethrower  

Gyarados @ Choice Band  
Ability: Intimidate  
EVs: 4 HP / 252 Atk / 252 Spe  
Jolly Nature  
- Crunch  
- Waterfall  
- Earthquake  
- Ice Fang  

Chansey @ Eviolite  
Ability: Natural Cure  
EVs: 248 HP / 8 Def / 252 SpD  
Calm Nature  
IVs: 0 Atk  
- Toxic  
- Seismic Toss  
- Stealth Rock  
- Soft-Boiled

[Black Waterfall]

@AverageJoe I just battle for fun so unfortunately I probably won't be of much help.

Anyway I just wanted to let you know that other users will give you better suggestions if you tell us what exactly is the metagame you have in mind 

[AverageJoe]

Oh of course, I want this for singles OU