vs Lorewalker Cho:
vs Dr. Ion Goldbloom:
vs Sully "The Pickle" McLeary
I had this combo of trainers but I don't recall off hand what teams I used but I tried to avoid my classic "Good" pets to save them for later.
Against the 4 legendary beasts I used some canned teams from my Pandaria legendaries:
vs Zao (the ox, who has a massive 990+ pt heal) a team of Zandalari raptors (3 of them, though I only needed 2) with Black Claw + Hunting Party finished him off quickly.
I did this with a raptor team too and it worked well. Not even sure you'd need the second raptor as my came in and just finished him off before his wish fired. Any decent pet should have been able to do that at that point. Two or three raptors is probably safer just in case something goes wrong and you don't manage to kill him off before the wish goes off.
vs Yu'la (dragon, who has no heal, but does have a lift-off evade/attack and low health), I used a classic explode team - enchanted lantern to cast sunlight, swap to a minfernal/netherspace abyssal and explode (make sure to use it in response to his lift-off!), then a darkmoon zepplin to explode. I am pretty sure I punched him once with the abyssal and missiled him once with the zepplin (and I think I decoyed with the zepplin, because I like to play it safe)
Gregarious Grell literally soloed him for me but there seem to be a few other good options. Feral Vermling should be pretty good and a Kun-Li Runt should be a good finisher.
vs Xu'fu (tiger, 3rd ability is a claw w/massive heal) I used the "classic" burst team - Val'Kyr (unholy ascension), Pandaren Water Spirit (Geyser, Whirlpool, dies before Water Jet casts), Chrominius (Howl, Surge of Power)
I used Tranquil yeti + Chicken + random mechanical pet. Open with Call of lightning. Swap in chicken and flock. For best results you want a bird that is still faster than Xu'fu with out the racial buff. When chicken dies bring back yeti and fist then Ion Cannon. Clean up with third pet if needed. Any Call of Lightning pet + chicken + Tonk/custodian should work. Call of lighting, swap pets, flock, when bird dies bring in tonk and Shock and Awe followed by Ion Cannon.
vs Chi-Chi I ran out of time before the server restart, I screwed up too many times to win in time. He always starts with his tranquility (heal over 2 turns) then an attack (his only attack is a 1-2 shot elemental, with +1 attack if he's faster, which he is) then his evade (100% chance to dodge for the turn it's cast on). He doesn't always cast Tranquility when it's available, but he always uses his dodge when it's available (so far as I've seen).
I used the "burst" team of valk, water ele, Chrominius for this one.
If you look at the teams I used 3 of the 4 rely on the same thing. The key is 100% dmg taken debuff is additive with the 50% less dmg taken buff so you end up at 50% more dmg taken. IE Ion cannon goes from 1000 to 500 because of the buff but goes up to 1500 after the debuff instead of back up to 1000. This is how the raptor team works, how the burst team works and how flock works. The exact pets aren't necessarily important in these strategies. It's all about getting around that damage reducing buff with a dmg increasing debuff.
For example the valk could be replaced by any undead with Curse of Doom now that you don't rez after the Unholy Ascension. You just need to make sure to use curse of doom on your rez turn so you die after you cast it or you screw up the timing. The Water spirit is the only option there but any pup/wolf/worg with howl should work in the place of Chrominius.
I'm sure there are other ways to do it it but these worked well for me.