Rockbiter, Stonechewer, & Acidtooth are Humanoids, so you'll want to use some Undead pets in this daily garrison pet battle, but you'll also want to think about a pet with Acquatic attacks. This is a very predictable fight, and you shouldn't have any frustrations with it if you stick to a team like mine.
My team included an Eternal Strider, a Restless Shadeling, and a Lost of Lordaeron.
Against Rockbiter, you'll start with the Eternal Strider (or a Mirror Strider or Aqua Strider - they all have the same abilities) by using Pump twice. Rockbiter will then submerge. Since you can't hit him anyway, you'll continue to use Pump and hit him on the second Pump when he emerges.
Then, you'll want to heal yourself (at least I did on the fifth round, it seemed to work well for the rest of the match) and then cast Pump twice more, and then finish off Rockbiter with a final Water Jet.
Your Strider should have around 500 to 600 HP left. The reason why the Strider is so good is because Rockbiter uses an ability called "Nature's Ward," which turns him into an Elemental and means your Strider's Aquatic damage is powerful.
When your second adversary, Stonechewer, comes out, I'd recommend using Healing Wave first and then Pump (twice). After that, your HP will be pretty low and you'll want to cast a last Water Jet. As long as your Strider is faster than 319, you'll hit Stonechewer first and get some valuable attacks in before your Strider dies.
Then you'll bring your Restless Shadeling out and cast Plagued Blood and spam Death Coil until Stonechewer is low and you can finish him off with a Shadow Shock or two. I prefer healing with the Death Coil to get Stonechewer low before using Shadow Shock. It seems to let your Restless Shadeling live longer until Acidtooth comes out.
Your Restless Shadeling should have enough life for a few rounds with Acidtooth, and I'd recommend using the same rotation. Plagued Blood, Deathcoil (maybe twice), and then Shadow Shock when the Shadeling is on its second life.
When your Lost of Lordaeron comes out, Acidtooth should be pretty low and around 400 to 500 HP. As long as he's that low, just ignore Curse of Doom and cast Siphon Life and Shadow Slash until Acidtooth dies. He won't live long enough for Doom to go off. You can probably get away with skipping Siphon Life, too, and just cast one or two Shadow Slashes to kill Acidtooth and end the battle.
Overall, a fairly predictable fight. The general movements will be (outside of unexpected crits and stuff):
Pump > Pump > Pump > Pump > Healing Wave > Pump > Pump > Water Jet (Rockbiter should die here) > Healing Wave > Pump > Pump > Water Jet (Strider dies, Restless Shadeling comes out) > Plagued Blood > Death Coil (about 3 times) > Shadow Shock (Stonechewer should die here) > Plagued Blood > Shadow Shock (once or twice until your Shadeling dies and you bring your Lost of Lordaeron out) > Shadow Slash (once or twice to finish off Acidtooth).
Now, I tried using the Lost of Lordaeron second and cast Curse of Doom on him, but Stonechewer actually died before Doom went off and my Restless Shadeling died at the same round as the other team, which meant a draw. Annoying! So my team works when you use Eternal Strider > Restless Shadeling > Lost of Lordaeron.
You could also use a Crawling Claw (which I don't have because Achaeology is a big piece of poo) or an Unborn Valkyr for your Undead teammates. Maybe a Blighthawk would work, too, with Infected Claw and Consume Corpse. I love fights where I get to use Undead pets!