Many of these pet battles wouldn't be nearly as troublesome if you didn't have to deal with two buffed extra pets after knocking them out; the boss pet will cast Fel Corruption throughout the fight while they're up, and in addition to being a fairly hard hitting AOE (and making it hazardous to have mechanical pets in your lineup), it turns the backline pets on their side into minibosses for up to 10 rounds.
Most of these battles I was able to get through with some experimentation, though for a few I had to hit the WoWhead comments for ideas on pets to try. It should be obvious from the chart that, although some of the commenters frequently push the Anklerender and the Emerald Proto-Whelp, I don't have the former leveled, and I only found the latter helpful once. I also tried out suggested strategies involving forced pet swaps (to minimize the Fel Corruption), but those gave me no success.
Due to the back line pets, setting up a traditional "Howl Bomb" (Unborn Val'kyer/Pandaren Water Spirit/Chrominius) frequently meant that the Fel Corrupted pets would finish off the AOE-damaged remaining pets even if the boss pet was dropped. Using 1.5-2 pets to get the boss pet down and cleaning up the remnants with the Anubisath Idol was ultimately more reliable.
TeamsThe numbers after the pet name are the ability slot choices - particularly with Chrominius and the Anubisath Idol, who saw heavy use, there are some fights where not swapping out an ability really hurt.
|Pet||Slot 1||Slot 2||Slot 3|
|Bleakclaw||Chrominius 2 1 2||Disgusting Oozeling 1 1 1||Crimson Geode 1 2 2|
|Chaos Pup||Iron Starlette 1 2 1||Pandaren Water Spirit 1 2 2||Chrominius 1 1 2|
|Corrupted Thundertail||Pandaren Water Spirit 1 2 2||Chrominius 1 1 2||Emerald Proto-Whelp 2 2 2|
|Cursed Spirit||Tolai Hare 2 2 2||Mr. Wiggles 1 2 2||Anubisath Idol 1 2 2|
|Dark Gazer||Lil' Deathwing 1 2 2||Infinite Whelpling 1 1 1||Anubisath Idol 2 2 2|
|Defiled Earth||Dancing Water Skimmer 1 2 2||Magical Crawdad 2 2 2||Anubisath Idol 1 2 2|
|Direflame||Garden Frog 1 2 1||Dark Phoenix Hatchling 2 1 2||Crimson Geode 1 2 2|
|Dreadwalker||Fel Flame 1 1 1||Infinite Whelpling 1 1 1||Anubisath Idol 1 2 2|
|Felfly||Chrominius 2 1 2||Disgusting Oozeling 1 1 1||Crimson Geode 1 2 2|
|Felsworn Sentry||Pandaren Water Spirit 1 2 2||Chrominius 1 1 2||Anubisath Idol 1 2 2|
|Mirecroak||Crow 2 2 2||Chrominius 1 1 2||Anubisath Idol 1 2 2|
|Netherfist||Unborn Val'kyr 2 2 2||Ghostly Skull 1 1 1||Anubisath Idol 1 2 2|
|Skrillix||Pandaren Water Spirit 1 2 2||Chrominius 1 1 2||Anubisath Idol 2 2 1|
|Tainted Maulclaw||Sprite Darter Hatchling 1 2 2||Darkmoon Hatchling 1 2 2||Anubisath Idol 1 2 1|
|Vile Blood of Draenor||Infinite Whelpling 1 1 1||Anubisath Idol 2 2 2||Crimson Geode 1 2 2|
Pet ListAnubisath Idol: The Anubisath Idol saw heavy use in Tanaan, making it into the lineup for 10 of the 15 battles. Sandstorm is the big boon here - the damage reduction and its humanoid healing allow it to survive the Fel Corruption-buffed backline pets.
Chrominius: Chrominius makes it into 7 of the teams in Tanaan, although in one he was a barely-used third pet. He is frequently paired with the Pandaren Water Spirit for the "Howl Bomb," buffing the Whirlpool/Geyser combination, but for the two flying pets, he can simply Howl + Surge of Power to one-shot them.
Crimson Geode: The Crimson Geode makes it into four of these fights, not so much for the boss pets but because it's a strong candidate for cleaning up flying pet adds.
Crow: Crow makes one appearance in Tanaan, using the Call Darkness/Nocturnal Strike combo on Mirecroak.
Dancing Water Skimmer: The Dancing Water Skimmer was brought in to handle the Defiled Earth.
Dark Phoenix Hatchling: The Rebirth ability helped make the Direflame fight doable for the team I was using.
Darkmoon Hatchling: There are other pets with the Predatory Strike ability, but the Darkmoon Hatchling is a Critter, which is less susceptible to Fel Corruption, so it survived on the backline to be brought in as a finisher on the Tainted Maulclaw.
Disgusting Oozeling: The Disgusting Oozeling was put into two lineups in case Chrominius couldn't for some reason handle the flying boss pets, but it turned out to be handy for cleaning up the back lines for them, since Fel-Corruption-empowered pets make fast work of a recharging Chrominius.
Emerald Proto-Whelp: The Emerald Proto-Whelp only turned out to be useful for me for cleaning up the Corrupted Thundertail's back line pets.
Fel Flame: Fel Flame was a trial pet in a lot of battles, but it only ended up on the final team for Dreadwalker - albeit as a starter, not on the bench.
Garden Frog: Garden Frog softened up Direflame enough for the phoenix to finish off - and the crowd control from the Frog Kiss didn't hurt to keep down the Fel Corruption casts.
Ghostly Skull: Bob was brought in for Netherfist; Ghostly Bite is lovely for how hard it hits, even with the boss damage reduction.
Infinite Whelpling: The Infinite Whelpling made it onto three teams; with its mixed bag of abilities, it's useful both on magic and mechanical pet bosses. The heal doesn't hurt, either.
Iron Starlette: Iron Starlette was one of the suggestions I got from the WoWhead comments; the Chaos Pup was giving me fits, and it turned out to be the mechanical for the job.
Lil' Deathwing: Dark Gazer was Lil' Deathwing's first appearance on a pet team for me. He is the hardest hitting dragon I've got, and many team combinations went down to this fight before he joined the team.
Magical Crawdad: Magical Crawdad is another pet you see touted a lot, and it can be quite good in some lineups, but for me it only helped with Defiled Earth.
Mr. Wiggles: Mr. Wiggles was brought in, as he not infrequently is, for an undead fight, the Cursed Spirit. Being a critter, he could take the Fel Corruption on the back line better, and he hit especially hard following up the rabbit.
Pandaren Water Spirit: The Pandaren Water Spirit made it onto 4 teams, most often as a truncated version of the "Howl Bomb," i.e., with no leading Val'kyr.
Sprite Darter Hatchling: The Sprite Darter Hatchling was brought in for Life Exchange versus the Tainted Maul Claw; it helped set up for Predatory Strike from the Darkmoon Hatchling.
Tolai Hare: The hare, like almost all the rabbits, can be wicked against undead pets, and it made the team for the Cursed Spirit as an armor break before Mr. Wiggles. Dodge and critter resistance to elemental damage didn't hurt.
Unborn Val'kyr: The Unborn Val'kyr made it onto only one team, versus Netherfist.
Alternate TeamsI'll update as I find additional combinations that work.
Direflame: Jungle Darter, Pebble, Crimson Geode