I still use the Thundering Pandaren Spirit for a massive injection of XP on a daily basis.
Until the daily battle quests were nerfed to one success a day, I used this guy to lvl something in the region of 250 pets and while you can only do him once daily so its still worth taking advantage!
Bring along your Safari Hat and both your +25 & +50% Bonus XP Treats.
I use...
Lil XT: with Zap, Heartbroken and Tympanic Tantrum
(Any) Hare: Speed 305 - Flurry Dodge Burrow
Plus the pet I want to lvl.
If you have a Mech or a Magic Pet to level then you can pile it at lvl 1
if your considering doing another pet then it wants around 650 HP to take a couple of hits off the Earth Elemental
Open with your lvling pet - let it take the Crystal Prison and the Rupture in the face, (Magic and Mech work well here because of their class benefits Mech's Res and Magic only take 35% HP in one hit) ...and will survive to be back-lined.
Swop to your Hare: Open with Flurry then dodge > take Crystal Prism in the face > Burrow > basically rince and repeat this on CD till the elemental is dead.
Swop to your XT for the Magic Pet: Open with Heartbroken > Tympanic Tantrum > finally Zap (XT will scrap a pass with 5HP before he Zaps the Magic pet -then he'll die from poison tick.
Swop to your Hare Flurry > Dodge > Pass > Burrow > Flurry 4tw
If Darnak the tunneller is still alive at this points dont sweat ...when he slams in to your Hare he'll kill himself and you'll win.
A lvl 1 Pet with +85% Bonus XP you pet will make ding around 15 levels (around 8400 XP).
Nice earner for 4 min's work.

Note: The Magic pet can RNG XT for a massive crit in the face... Oh well! Just heal and go again!
The RNG Monkey is always watching! :p