I know dude... I even wrote I got 8-9k per battle (level 1-5 pet vs enemy level 1-2 pets). Still level 35 - 80 in one hour? That sounds pretty ridiculous. ANd I still have a hard time finding anywhere with enough pets.
On my full heirloom hunter and the 300% xp gain elixir (1 hour buff) I managed to go from lvl 40 to 83. Far from optimised - I fooled around in Orgrimmar when I probably should have gone silvermoon instead. But either way, pretty ridiculous xp gain.
As per the Warcraft twitter, they are aware of the issue and it is not intended. A hotfix is being prepared and I suspect it will be implemented shortly on EU as the servers are going down in 5 minutes.
The level of your pet determine what level pet you must kill to gain experience. I just did it with my lv 9 pets vs 2x lv 6 squirrel and it gave me 80k xp at lv 85 which is like half of a mop quest)