Sprouts is an elemental. Prince Charming is aquatic. Runts is a beast.
These pets are pretty easy to beat with the right match ups. I used Garden Frog against Sprouts, alternating between Frog Kiss and Healing Wave on cooldown. I used Blue Dragonhawk Hatchling against Prince Charming, just repeating Quills over and over. Finally, against Runts, I used the Clockwork Gnome.
Rockbiter has a skill which makes him take damage as if he were an elemental instead of humanoid pet. Using Scourged Whelpling first, cast the Dreadful Breath until the Scourged Whelpling dies. Rockbiter will be nearly full health, but the other two opponent pets will be nearly dead when your Scourged Whelpling dies. Summon your aquatic pet when Scourged Whelpling dies to defeat Rockbiter, then switch to your last undead pet for the other two. I used the Magical Crawdad for the aquatic pet, opening with Whirlpool, then Renewing Mists, then Surge until he died (using Whirlpool and Renewing Mists on cooldown). After Rockbiter dies, just bring out the Macabre Marionette (or any undead pet) and finish off the Stonechewer and Acidtooth.
When Tirs comes out, his first skill will always set the weather to cleansing rain. This makes the Scourged Whelpling and its Dreadful Breath skill ideal for your opening pet. Just cast Dreadful Breath until the Scourged Whelpling is dead. Then pull out the Pandaren Water Spirit and do Geyser, followed by Whirlpool. Switch to Chrominius for Howl and Surge of Power. Sometimes (actually, almost always) Tirs will one shot the Pandaren Water Spirit and you have to switch to Chrominius and finish off Tirs with Howl and then repeating Arcane Explosion until he dies, saving Surge of Power for Fiero. Then, your Surge of Power should be enough alone to defeat Fiero.
You can also beat this team using a Scourged Whelpling casting Dreadful Breath until he dies and then using Death Talon Whelpguard to finish off both Tiers and Fiero. Just use Whirlwind on cooldown and Shadowflame.
This little guy is pretty tough. I use the Garden Frog, casting Frog Kiss until the goat does its super strong charging skill (which kills the frog). Then pull out the Pandaren Water Spirit and cast Geyser the first turn and Whirlpool the second before switching to Chrominius. Chrominius does his Howl on his first turn and then finishes the goat off with Surge of Power.
I used the Scourged Whelpling first, and cast Dreadful Breath until he died, then switched to the Emerald Proto-Whelp and finished them all off with it. I think you could beat this team with just the Emerald Proto-Whelp, but it’s more fun to sacrifice the whelpling for the aoe damage.
For this pet battle, I used a Crystal Spider, Darkmoon Tonk, and Emerald Proto-Whelp. I killed Grubbles and Scrags with the spider and then switched to the proto-whelp for the flying Stings. Had the spider not survived Scrags, Darkmoon Tonk was there for back up.A team consisting of an Arctic Fox Kit, Clockwork Gnome, and the Emerald Proto-Whelp works nicely also.