Still working after 8.0 :) super easy

Magical Mayhem
Magic Lantern 1,2,2
Magic Broom 2, 1, 2
Legs 2, 1, 1
Magic Lantern Opens with
Flash
Light
Beam
Beam
Flash
Beam
Beam (probably dies on this round but may get another Beam)
Magic Broom comes in
Sand storm
Wind up
Wind up
Batter (Broom dies)
Legs comes in. If Gnasher > 300 health then Focus Beams else kill him with Surge of Power

If interested for flyers I used.
Junglebeak 2,2,1 Flyby, Liftoff, Peck. Flyby on last move if possible adds to Ikky's damage
Ikky 1,1,1. as above. Got him down to 38.
Crackers 2,2,1 or any flying would probably work to finish him off.

TD Script

ability(Curse of Doom:218)
ability(Haunt:652)
ability(Flock:581) [enemy.aura(Black Claw:918).exists]
ability(Black Claw:919)
change(next)

Just an option, after Haunt, brought in a level pet, then swapped to Ikky, seemed to not effect result.

I did this with a level 21 level pet. I got 270 xp, both the other pets died and I had to finish the fight with the level pet so that was 270 xp in total, unshared. Really not worth bothering with low level pets on Argus.

Tried the critter strat listed. Don't have the spring rabbit. Came close once. That bleed damage gets you. Came closest using sneaky marmot instead of fawn.
Will try again when I level a spring rabbit.
His speed is 328 so best to be faster. He hits hard sometimes 1200 +
Did solo this with Anklerender 341 speed. Bleed got him at end but was all I needed to win.
Thanks for all the strats and help everyone :-)

I have done this several times. With the mentioned Anklerender.
Black Claw,Hunting party, Leap and done every time so far.
Anklerender dies at end, suppose you could put a couple pets below 25 in other slots
might get some exp. out of it. Haven't tried that myself.

Experimented some with a couple of teams:

Gnasher - Beasts

1: Kovok (1,2,1)
2: Zandalari Anklerender (2,2,2)
3: Zandalari Kneebiter (2,2,1)

Turn 1: Black Claw
Turn 2: Poison Fang
Turn 3; Switch to Zandalari Anklerender
Turn 4-5: Hunting Party

Gnasher - Aquatic

1: Spineclaw Crab (1,1,1)
2: Ironclaw Scuttler (1,1,2)
3: Juvenile Scuttleback (2,1,1)

Turn 1 Spiny Carapace
Turn 2 Whirlpool
Turn 3 Rip
Bring in Ironclaw Scuttler
Turn 1 Blood in the Water
Turn 2 Rip
Bring in Juvenile Scuttleback
Turn 1 Dive
Turn 2 Claw

Gnasher - Dragons

1: Chrominius (1,1,2)
2: Soul of the Aspects (1,2,1)
3: Blue Dragonhawk Hatchling (1,1,1)

Turn 1 Howl
Turn 2 Bite
Turn 3 Surge of Power
Bring in Soul of the Aspect
Turn 1 Deflect (Maul is off cooldown)
Turn 2 Surge of Light
Turn 3 Claw
Turn 4 Claw
Turn 5 Deflect
Turn 6 anything
Bring in third pet
Turn 1 kill Gnasher...

Gnasher - Elementals

1: Cinder Kitten (2,2,1)
2: Skunky Alemental (2,2,2)
3: Core Hound Pup (1,1,2)

Turn 1 Leap
Turn 3 Prowl
Turn 4 Leap
Turn 5 Rend - Cinder kitten dies, bring in Skunky Alement.
Turn 1 Explosive Brew
Skunky Alement dies next turn. Bring in Core Hound Pup
Turn 1 Howl
Turn 2 Scratch
Turn 3 Burrow or scratch depending on the enemy health.

Gnasher - Flyers

1: Ikky (1,1,1)
2: Direbeak Hatchling (1,2,1)
3: Bloodgazer Hatchling (2,1,1)

Turn 1 Curse of Doom
Turn 2 Haunt
Bring in Ikky
Turn 3 Black Claw
Turn 4 Flock

Gnasher - Humanoid

1: Corefire Imp (2,1,2)
2: Flayer Youngling (2,2,2)
3: Flayer Youngling (2,2,2)

Turn 1 Wild Magic
Turn 2 Immolation
Turn 3 Rush
Turn 4 Wild Magic
Bring in Flayer Youngling
If Maul is up use Deflection, otherwise use Triple Snap.

Gnasher - Magical

1: Jade Owl (2,1,1)
2: Sanctum Cub (2,2,2)
3: Brightpaw (2,2,2)

Turn 1 Adrenaline Rush
Turn 2 Lift-Off
Turn 3 Trash
Turn 4 Adrenaline Rush
Turn 5 Trash
Bring in Sanctum Cub
Turn 1 Black Claw
Turn 2 Rend
Turn 3 Leap
Turn 4 Rend
Kill off wiith third pet is needed.

Gnasher - Mechanical

1: Tranquil Mechanical Yeti (2,1,1)
2: Stonegrinder (2,2,1)
3: Trigger (1,2,1)

Turn 1 Call Lightning
Turn 2 Super Charge
Turn 3 Trash
Turn 4 Trash - Ressurects
Turn 5 Trash - dies
Bring in Stonegrinder
Turn 1Super charge
Turn 2 Woodchipper - ressurects
Turn 3 Woodchipper - dies
Bring in Trigger
Turn 1 Overtune
Turn 2 Burrow

Gnasher - Undead

1: Infested Bear Cub (2,2,2)
2: Unborn Val'kyr (1,2,1)
3: Cursed Birman (2,2,1)

Turn 1 Roar
Turn 2 Corpse Explosion
Bring in Unborn Val'kyr
Turn 1 Curse of Doom
Turn 2 Shadow Slash
Turn 3 Haunt
Bring in Cursed Birman
Turn 1 Spirit Spikes
Turn 2 Spirit Claws
Turn 3 SPirit Claws

Gnasher - Critter

1: Gleamhoof Fawn (2,2,2)
2: Spring Rabbit (2,2,2)
3: Arctic Hare (2,2,1)

Turn 1 Nature's Ward
Turn 2 Headbutt
Turn 3 Stampede

Turn 1 Dodge (for Maul)
Turn 2 Stampede
Turn 3 Flurry

Turn 1 Flurry
Turn 2 Dive (if needed)

Good list, but you mention Curse of Doom and Haunt with Flyers. None of the pets you list (or, indeed, any flyers) have those abilities. Granted, all you really need is Ikky and the Black Claw / Flock abilities.

I didn't have your Undead pets so I used these instead:
Infected Squirrel (2,1,2), Unborn Val'kyr (1,2,1), Risen Saber Kitten (2,1,1)
1. Rabid Strike
2. Corpse Explosion
Bring in Val'kyr
3. Curse of Doom
4. Shadow Slash
5. Haunt
Risen Saber Kitten
6. Rake
7. Devour

Easy down with Zandalari anklerender 2-2-2,footslasher 2-1-2 and kneebiter 2-2-1 :)

didn't even need 2nd pet using this strat

Dragon strat
Nether Faerie Dragon 2 2 1
Emmigosa 1 2 1
Chrominius 1 1 2
NFD Moonfire Life exchange Arcane Blast x 2 Moonfire NFD dies
Emmigosa Claw Surge of power
Gnasher should die now, if not surge of power again with chronimius

Super easy strat. Thank you! Never had to use Chrominius.

Thanks! This worked perfectly, even with Gnasher critical hitting twice

ability(218)
ability(652)
change(#2)
ability(919) [self.round=1]
ability(581)

I used the two pets above but didn't use Haunt, but Curse of Doom. Worked perfectly and was dead after 3rd round. Curse ended up killing him.

For the Achievement "Beast Blitz" I would recommend using Zandalari pets, simply use black claw and then hunting part to kill the boss in 2-3 turns, easy!

Worked perfectly! ty <3