Hazelnuttygames has a guide on Youtube that isn't relaint on howlbomb. I think the hardest is Zao, Calfling of Niuzao. From her guides, I realized Mr. Bigglesworth can solo Yu'la:
1: Claw
2. Ice Tomb
3. Ice Barrier.
4: Pass
5: Claw
6: Claw
Repeat 1-6 until Yu'la's down.

Does anyone know if the Celestial Tournament gives viable experience to level pets on? The reason I ask is you can defeat the first 3 tamers, leave and requeue.

My testing on the ptr leads me to conclude that pet charm rewards are cut in half. Garrison daily gives 3-5 charms rather than 7-10 I get on live. Tamers reward 2 instead of 4. I only did 1 Tanaan jungle fight, but the difficulty I encountered made it not worth doing when it goes live. No gold rewar...

It can be a little bit easier, though also a bit more RNG dependent since he used Rupture instead of Deflect.

This is a strong team. The only time I have trouble is against Anubisath Idol. I frequently seem to get someone who runs 3x Idols with 3x sandstorm. Sandstorm completely negates Immolation, so the Imp can't heal in the back row. I had to turn to a Graves team to take that team down.