What is bad about it is the fact that once you have the Tamer title (and the pet from bags if you are a collector) there is really no reason to fight trainers anymore. They are too hard to boost pets and theres not enough reward for killing them a 2nd time. If they were easier or the level cap of ur pets were higher so that they got easier over time you would want to boost low level pets on trainers to get the maximum xp. The only problem I see with this would be that players "farm" trainers rather than go into the wild but considering that you can only fight them once a day it that problem wont even exist.
Undeads may be weak against critters but lets get real, almost no one uses critters in pvp (trainers dont really use them either) which makes these types extremely overpowered. I have lost more than 20 matches because the enemy had an undead pet, while my pets are not weak to undead I have to kill them twice to win the battle and that is just a huge deal.
This is not true some pets can use ability X and Y in slot 2 and 3 while another pet has ability X and Y in slot 2, thus making one of the pets much better than the other for no reason at all. I dont know if its a bug because theres not many of these examples but they do exist and that is a huge problem imo.
I started farming as the first person on my server, I was litterally amongst the only 5 people who got to halfhill in time to start farming on the very first day and I were probably the only person who knew wtf was going on with halfhill. Here we are today 3 weeks later, I have yet to get a Terrible Turnip by myself. I bought one of the very first Terrible Turnips on the server 10 days into the expansion and by then it was too late for it to be as useful as I would have liked it to be.