Ghostcrawler posted in the WotLK Beta hunter forum today that the amount of experience that pets needs to level is being reduced:
We just recently increased the pet level rate.
Pets needed 1/16th of hunter experience to gain a level, but don’t benefit from quests or rest. Those two account for a lot of experience, especially at higher levels (where quest content tends to be denser).
We changed the experience needed for 1/10th. You should notice a big jump in pet level rates.
I am not sure if that change got in the most recent data push.
I did a quick test in game and verified that yes, this change is in build 9014.
Astute readers will notice a small problem with Ghostcrawler’s post, by the way. 1/16th of hunter experience is actually less than 1/10th. I believe this is a simple typo; previously pets needed 1/6th of hunter experience, which is around 16%. 1/10th of experience is, of course, 10%. Ghostcrawler may have started with typing the percentages and then changed it fractions, or just had a (as they say) brain fart.
At any rate, pets in the beta/PTR now level 60% faster than they do on live.
This isn’t the ideal solution to my way of thinking; I’d much prefer that pets benefit from quest and rest XP. But this is a solution, and considering the other pet problems that need to be dealt with right now I am quite happy to see this change happen!