For the Thundering Pandaren Spirit, the following is a strat that I found and started using. I have not lost once yet, and have beaten him with the first two of the lineup multiple times without having to use the 3rd pet. Hope this helps some of you.
Thundering Spirit line up: [lvl 25 Rares]
1. Elfin Rabbit (2,2,1)
2. Emperor Crab (1,1,1)
3. Clockwork Gnome (1,1,1)
vs Pandaren Earth Spirit:
- Burrow > Dodge > Flurry
- From here on cast Burrow > Dodge when off cooldown and use Flurry as filler untill Earth Spirit is dead.
vs Oily Slimeling:
- Continue same exact rotation with your Rabbit on the Slimeling until your Rabbit dies.
- Switch to Emperor Crab
- Shell Shield > Renewing Mists > Snap
- From here on, recast Shell Shield and Renewing Mists when each has only 1 charge left on the buff, using Snap as a filler until Slimeling is dead.
vs Darnak the Tunneler:
- Continue using Emperor Crab rotation until Darnak or your Crab is dead.
- If your crab dies, chain cast Clockwork Gnomes Metal Fist until Darnak dies.