Here is my pet levelling team and a TD script to use it. I run this against the Icespine Hatchlings in Frostfire Ridge. It typically takes them out in 7 turns and I can run it at least a dozen times before needing to Revive/Bandage. The only caveat is that your levelling pet needs to be level 3-4 before you start.
Levelling
1: Rotten Little Helper (1,1,1)
2: Leveling Slot
3: Rotten Little Helper (1,1,1)
_3::11141A5:ZL:11141A5:
ability(Booby-Trapped Presents:1080)
ability(Greench's Gift:1076)
change(#2) [!self(#2).played]
change(#3) [self(#2).active]
ability(Club:1079)
For help with scripts, see Xu-Fu's page below.
https://www.wow-petguide.com/index.php?m=TDScripts