This NPC is in Dragonblight.
Information taken from the comment on WoWhead.com.
His pets: Dragonkin, Undead, Undead
1.) Anubisath Idol (Crush, Sandstorm, Deflection) Qiraji Guardling (Crush, Sandstorm, Blackout Kick). Use against the first two. Idol is preferred because there’s less RNG dependence. Keep up Sandstorm and spam Crush. For the Idol, use Deflection against Lift-off. For the Guardling, use Blackout Kick whenever it’s up.
2.) Any critter with Scratch + Swarm + a self-heal (I used a Marsh Fiddler). Use this against the third one. Scratch until Sandstorm ends, then Swarm for the win.
3.) Leveling pet. Make sure it has at least 600 hp. Swap in on the second pet, then swap out again immediately.