I find it hard to get guides which tell you explicitly which pets you need to defeat which tamer. I am not too good at remembering which pet is strong or weak against another, so I hope this might help you decide too.
Mo’ruk is located near to the Anglers Warf and The Incursion. His hang out place looks pretty cool. Lots of fun inflatables!
Anyway, his 3 pets are: a rather cute Jungle Grub, a Luyu Moth and the Wanderer’s Festival Hatchling. The team I used to beat them are:
..with those abilities shown.
It took a couple of tries to get the order of abilities right. The grub (the first pet up) always burrows on the second go, so that’s when I built my rocket, then released it after it had burrowed, ensuring I didn’t waste it. This did enough damage so all I had to do was punch him in the face and he was dead.
The moth didn’t do a huge amount of damage compared to the others, but with all the poisons the damage over time was pretty harsh. Slicing wind and moonfire from the Nether Faerie Dragon handled it ok. Finally, the Hatchling does a pretty powerful powerball type ability which does some damage, but I dotted it with the poisons and after a couple of slicing winds from the Glowfy it was dead.
As always, I’m not an expert by any means, but these pets will do the job if you’re not looking to power level another at the same time.