Using just pet battles, I recently leveled my alt warlock from about halfway through level 85 to 90 over the last few weeks. I didn't keep perfect track, but it was between 130 and 150 battles for each level. I leveled in the Jade Forest at the Jade Temple Grounds. I chose this spot because it has a fair number of Temple Snakes (level 23 to 25) that respawn pretty reliably and I had more beasts to be upgraded than anything else, and I figured I could get a fair number of battle-stones.
After dinging 86, 87, and then 88 without a single battle-stone dropping I thought I was just incredibly unlucky, that's close to 400 battles by my calculations. When I got four battle-stones in the time it took to get halfway through level 88, I thought maybe my luck had turned around. Yet I didn't see another battle-stone at all from then to level 90, probably another 200 battles or so.
This got me thinking about the battle-stones I did see. When I first started leveling through pet battles, I figured it would be a good way to level up a bunch of my lowbie pets. I started at the bottom, my lowest-level pets would get leveled, switching out for another after each battle. I made pretty good progress through my lowbies, and by the time I had reached level 88 on my warlock, my lowest-level rare pets (I wasn't going to level anything but rares) were levels 5 and 6.
It was at this point that I had decided to change my daily trainer habit. I was going to make a team of two level 25 pets to carry a lowbie through on each of the tamer battles. This meant I had to level about a dozen pets to level 25. Over the next few days I leveled these pets to 25 while leveling my warlock at the same time. This is the only time during the whole grind to 90 that I got any battle-stones at all. Each of the pets I leveled to 25 started out at around level 16, and I leveled each pet to 25 before switching to the next.
After I had leveled those pets to 25, I switched back to my previous method of leveling my lowest-level pets, and didn't see a single battle-stone for a level and a half.
Perhaps I'm just paranoid or trying to see a pattern that isn't there, but I haven't seen a single battle-stone when leveling a pet that is far lower than the team I'm battling. Has anyone else leveled a lot of their lower-level pets in this way? Have you had the same experience? Or is it that I'm incredibly unlucky and it's a coincidence?