This fight may be challenging at first, if you're not get used to its mechanics. But with a bit of luck you can even fight with just two 25lvl pets and upgrade one 1lvl battle pet :)
The best match i've found to fight this master is the following:
Flayer Youngling: Blitz, Reflection, Rampage.
Moth: Alpha Strike, Cocoon Strike, Moth Dust.
The description of the fight is down below. TL; DR? This is a recap:
Against Chirrup, use your Flayer Youngling, 3x Rampages, Chirrup dies. Against Stormlash, keep using FY: Reflection, Blitzs x2, Rampage. Your FY will die, bring up your Moth. Alpha Strike against a low life Stormlash, the dragon will die. Another Alpha Strike or Moth Dust, Whiskers uses Dive; Cocoon Strike, so you take no dmg, then Alpha Strike it to death. Congratulations! You just defeated 3 legendary pets with just 2 of your rare pets :P
The fight will be like this:
Starting vs.Chirrup, use a Flayer Youngling (Terokkar Forest, lvl 16-17): Chirrup will start with Swarm, which does few damage. If you use Rampage, you can beat it in those 3 turns Swarm is active.
Then, here it comes Stormlash, which hits very very hard, and you'll still have the Swarm debuff active on you, so... 50% more damage taken and things can get very nasty for most pets, but not for your Flayer Youngling hehe. Use Reflection and you'll avoid about 900 dmg or more, also hitting Stormlash back :). After that, Stormlash will use Roar, you can use Blitz and here it's when luck enters the fight, because Blitz can hit one or two times, and only one hit won't be good enough. But still, keep using Blitz until your Rampage skill is up again, then use Rampage. Stormlash will keep using its Tail Sweep after Roar, just get on with it.
Stormlash will end low life when your Flayer Youngling dies (and if it fails one Tail Sweep, your FY will live past this enemy haha), and its the turn to use your Moth. Hit him with your Alpha Strike and the dragon will die.
Finally, its the turn of Whiskers, which will start using Dive. You strike first, and here I prefer to use Moth Dust (not always works, but if it does the figh will be much shorter). Then, as Whiskers is Diving, you use Cocoon Strike to avoid the dmg. Afterwards, Whiskers will keep using Surge, and you use your Alpha Strike. When Whiskers is low life, it will use Survival. And with "low life" I mean when your next hit will kill it for sure, and this way, its life will be reduced to 1.
Now, there are various ways to enter a 1lvl pet to upgrade it. You can use it in your first turn, against Chirrup, and your pet will take very few damage, but I dont recommend it, because it will make that fight looong and boring. You can also wait until Whiskers is at 1 point HP, after you strike it in Survival, then wait till it kills your moth and then kill it with your 1lvl pet, but... sometimes your pet will fail, and die of Surges.
So, whats the best option? A good timing. You know that if Whiskers is around 300-500 HP, it will use Survival, so thats your turn to change pets: you bring up your 1lvl pet, Whiskers uses Survival and your low pet receives no damage at all, then change it back to moth and finish it :)