He is ONLY tamer without fixed pattern (his snake and moth doesn't have fixed pattern, but his scarab does) and hard to 2v3 atm.
But, here is ultimate solution with near-RNG proof 2v3 combo to beat that uldum guy for you fellas :)
Emerald Proto-Whelp (pref breed 4 for higher block + more dmg) + anything that can solo the snake
Basically, Emerald Proto-Whelp is going to kill both moth and scarab. With his Emerald Presence, he takes VERY LITTLE amount of damage from both of them. Both Moth and Scarab deals small damage multi-attacks like Slicing wind and Flank. Since Emerald Presence blocks about 90~ish damage per hit, their attacks are going to be nothing but a mere scratch. It will take some time as he will have to use his 3 turn healing ability to shrug off the damage time to time, but it removes RNG factor by whole lot.
As for snake, if he didn't have counter strike and Vicious Fang, Proto-Whelp can literally solo all 3 of his pets. Unfortunately, he does pack both counter strike and Vicious Fang, and you would have to kill the snake with different pet. (just take out FFF or something)
It would be IDEAL for him to start up with Snake -> Moth -> Scarab.(saves the switching turns) But it really doesn't matter what he starts up with.
If he starts up with Snake, just do supercharge-> wind-up -> wind-up to kill his snake.
On his moth, switch to your exp soaker to soak his moth dust to reduce the potential RNG crisis. (make sure his lvl is high enough to take ATLEAST one dust hit. should b like..lvl 10ish?)
If he uses cocoon strike first, just stay in and soak the dust next turn (if he can)
Once that's done, take out your proto-whelp and proceed to grind it down after setting emerald presence up.
If he starts up with moth, just use that turn to charge up your FFF and switch to your Proto-whelp to kill the moth, switch to FFF on snake, kill the snake with wind-up, than do your magic against FFF. After that, you have two choices. Use FFF to finish the scarab fast or safely grind it down with your proto-whelp. If you want to use FFF to kill this thing you gotta avoid getting hit by hiss.
On scarab, he will ALWAYS use apocalypse -> hiss -> flank spam. If you are trying to kill his scarab with FFF, don't get hit by his hiss. Soak that with your exp soaker than switch back to FFF to finish it up with wind-up -> wind-up