To be quite frank, Assault Vest isn't a good item on Samurott because it doesn't have the best offensive power or the best special bulk. For physical Samurott, it's better off setting up Swords Dance boosts, as 100 Attack, as I mentioned, isn't the strongest. Shell Armor is a rather situational ability as well.:
-Swords Dance
-Waterfall
-Megahorn
-Aqua Jet
Nature: Adamant
EVs: 160 HP/252 Atk/96 Spe
Item: Life Orb/Lum Berry
Ability: Torrent
or
-Hydro Pump
-Ice Beam
-Grass Knot
-Taunt/Aqua Jet/Superpower/Knock Off
Nature: Modest/Rash
EVs: 4 Def/252 SAtk/252 Spe
Item: Life Orb
Ability: Torrent
As weird as this sounds, Unnerve is the better ability for Pyroar to use, as berries see niche use. Rivalry is too inconsistent and Moxie is useless on a special attacker like Pyroar. Hyper Beam is a bad move competitively because it leaves Pyroar a sitting duck the next turn. Fire Blast is also the preferred Fire STAB, as it still has acceptable accuracy:
-Fire Blast
-Hyper Voice
-Hidden Power (Grass)
-Will-o-Wisp/Flamethrower
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Life Orb/Choice Specs
Ability: Unnerve
or
-Fire Blast/Overheat
-Flamethrower/Overheat
-Hyper Voice
-Hidden Power (Grass)/Endeavor
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Choice Scarf
Ability: Unnerve
Setting up Shell Smash and Stealth Rock is just making Crustle do too much at once. Having Earthquake as your lone offensive attack means that Crustle will be walled by Flying Pokemon, a type that it handles very well normally. Sturdy is also the superior ability on Crustle, as it ensures that it can do something from full health:
-Stealth Rock
-Spikes
-Rock Blast
-Knock Off
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Red Card/Mental Herb/Custap Berry
Ability: Sturdy
or
-Shell Smash
-X-Scissor
-Stone Edge
-Earthquake
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Life Orb/Lum Berry/White Herb
Ability: Sturdy
However, you can also consider Sandslash as an alternate hazard setter, as it also provides Rapid Spin support for Pyroar:
-Earthquake
-Knock Off
-Rapid Spin
-Stealth Rock
Nature: Adamant/Impish
EVs: 172 HP/252 Atk/84 Spe (Adamant) or 252 HP/252 Def/4 SDef (Impish)
Item: Lum Berry (Adamant)/Leftovers (Impish)
Crustle and Pyroar share a weakness to Water and Samurott isn't enough to cover for this. What you need is a Grass Pokemon to cover that weakness. Examples are Gourgeist (Super Size), Gogoat, Lilligant, Tangela, and Quilladin (either one should go over Weezing):
Gourgeist:
-Will-o-Wisp
-Leech Seed
-Synthesis
-Foul Play/Seed Bomb
Nature: Impish
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
Ability: Frisk
Gogoat:
-Bulk Up
-Horn Leech
-Earthquake
-Substitute
Nature: Adamant
EVs: 252 HP/4 Atk/252 SDef
Item: Leftovers
Ability: Sap Sipper
Lilligant:
-Quiver Dance
-Giga Drain
-Hidden Power (Fire)/Nature Power
-Sleep Powder
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb/Miracle Seed/Meadow Plate
Ability: Chlorophyll
Tangela:
-Leaf Storm
-Giga Drain/Ancient Power
-Hidden Power (Fire)
-Sleep Powder
Nature: Modest
EVs: 252 HP/4 Def/252 SAtk
Item: Eviolite
Ability: Regenerator
or
-Giga Drain
-Hidden Power (Fire)
-Sleep Powder/Toxic
-Leech Seed/Synthesis
Nature: Bold
EVs: 252 HP/252 Def/4 SDef
Item: Eviolite
Ability: Regenerator
Uxie can also act as the team's hazard setter if you didn't opt for Sandslash or the hazard-setting variant of Crustle:
-Stealth Rock
-Psychic
-U-turn
-Thunder Wave
Nature: Relaxed
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
If you did opt for Sandslash or the hazard-setting Crustle, here's a better take on Calm Mind Uxie. Signal Beam lets it deal with Dark Pokemon, while Giga Drain provides recovery:
-Calm Mind
-Psyshock
-Signal Beam
-Giga Drain/Hidden Power (Fire)
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Leftovers