I hadn't found similar topics - if they exist pls delete this one.
So as you know - people who had defeated battle-pet tamers can repeat fight and gain huge amount of pet experience only by making daily quests (they cannot be refreshed or re-taken) - but there is a bug and you can gain experience from 1 daily quest as many times as you want.
What to do:
1) take daily quest
2) begin the fight with battle-pet tamer for example with Lydia Accoste - NPC - World of Warcraft
3) when you defeat 2 of 3 pets - queue to random scenario, arena, bg etc.
4) when your scenario queue pops up - defeat the last pet
5) when your pets will gain experience immediately enter scenario (as for me - i prefer join arena and after the end i repeat quest) and then leave
6) you can repeat the fight and lvl up your pets as many times as you want