Rate my [Gen 9] National Dex AG team (first timer)

Question

This is my first ever post on Pokebase, and I am a beginner at making competitive teams, so I will probably need a lot of advice. This team had pokemon that I like, and that I think would make a decent team. (I might be completely wrong.)
Also, if my submission format is wrong on any way, please tell me as well.

Format: [Gen 9] National Dex AG

Metagross-Mega @ Metagrossite
Ability: Clear Body
Tera Type: Steel
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Meteor Mash
- Zen Headbutt
- Earthquake
- Ice Punch
Metagross is for just attacking. Meteor Mash and Zen Headbutt are typically used for physical STAB, and Earthquake and Ice Punch for coverage.

Jirachi @ Assault Vest
Ability: Serene Grace
Tera Type: Steel
EVs: 224 HP / 252 Atk / 32 Spe
Lonely Nature
- Iron Head
- Zen Headbutt
- Aura Sphere
- Thunder

Jirachi is basically the same as Metagross, but Iron Head, Zen Headbutt, and Thunder are used for pairing with the Serene Grace Ability.

Dialga-Origin @ Adamant Crystal
Ability: Pressure
Tera Type: Steel
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Flash Cannon
- Roar of Time
- Earth Power
- Dragon Pulse

I think that the Steel-Dragon type combination is strong. Flash Cannon and Dragon Pulse are the main special STAB moves, with Earth Power for coverage. Roar of Time might be helpful for I'm certain situations that need a lot of damage done.
The first three pokemon are all similar, so using them three in a row isn't a good idea in my opinion. (Or I should just ditch 1-2 of them.)

Samurott-Hisui @ Leftovers
Ability: Torrent
Tera Type: Water
EVs: 252 HP / 252 SpA / 4 Spe
Modest Nature
- Hydro Pump
- Dark Pulse
- Ceaseless Edge
- Megahorn

The Dark Type Samurott would have Hydro Pump and Dark Pulse for its main moves, with Ceaseless Edge's spikes probably going to be useful as well. Megahorn is for coverage, specifically against Psychic.

Talonflame @ Rocky Helmet
Ability: Flame Body
Tera Type: Fire
EVs: 252 Atk / 4 SpA / 252 Spe
Naive Nature
- Fire Blast
- Brave Bird
- Return
- Roost

Fire Blast and Brave Bird are the main moves, with Roost to heal if needed. Return is kind of a filler move...

Hydreigon @ Life Orb
Ability: Levitate
Tera Type: Dark
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Draco Meteor
- Dark Pulse
- Thunder Wave
- Nasty Plot

Finally, another pseudo-legendary, Hydreigon. Draco Meteor and Dark Pulse are for special STAB, and Thunder Wave is too make up for the lower speed stat (I got that off of someone else). Nasty Plot is helpful to raise Sp. Attack.

With my lack of strategy and type coverage, I would like to get a lot of feedback for my first ever post ;)

Comments

I would recommend changing H-Samurott's ability to Sharpness and giving it Razor Shell/Aqua Cutter to replace Hydro Pump as its water STAB since it functions better as a physical attacker. Megahorn to cover for psychic types is pointless since Ceaseless Edge already does that. Change leftovers to either an offensive item like Choice Band or Scarf, or Focus Sash since H-Samu won't be able to stick around for long. Same deal with Talonflame, Flare Blitz instead of Fire Blast, and replace Return with either Defog or U-turn. Also, Rocky Helmet is not very useful on it, use Heavy-Duty Boots instead, because it takes an unholy amount of damage from Stealth Rock. Jirachi's set is quite unorthodox. I get that you're trying to do something akin to Paraflinch, but a better set would be Iron Head, Body Slam, Stealth Rock, and U-turn. If you're just looking for something that does damage, then you can replace Stealth Rock with Zen Headbutt. Dialga-Origin wants Draco Meteor instead of Roar of Time, since you almost never want to be stuck doing nothing in a turn. Aside from Hydreigon, your team lacks setup sweepers, so you might find it hard to break through defensive cores. Consider Hone Claws for Metagross, though that not might be worth a move slot.
I do have to ask though, why Hydreigon and Dialga instead of pokemon like Koraidon and Miraidon, who can fulfill similar roles but better? Also, I don't play AG a lot, but Talonflame and H-Samurott are pretty frail and either have low attacking stats or are rather slow, and don't seem fit for HO playstyles in AG, though correct me if I'm wrong.

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Thanks! If it tells you anything, I started playing with Ruby, and never learned much about the newer generations. I see the advice though, thanks! :)

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Hisuian samurott should be physical. get choice scarf, use tera fighting and use sacred sword instead of megahorn.

This set worked really well for me

Also I feel like there are much better pokemon to use than things like talonflame and hydreigon. I'm not an ag player, so maybe look into the current meta?

Hope i helped!