The real issue with woodland, druids and predators is that there's no scaling. There's only one tier of that trait and that's it. How do you balance that around other traits that have 3 tiers? Furthermore, these traits have only cost 1 and 2 units, which is ridiculous. That means that you can literally complete the sets from the first round. So how do you balance it? Do you make it weak to match the bronze tier of other sets, or do you make them so strong so that they match gold tier sets in the lategame. Seems like Riot tried to make an in between case that's obviously not working really well.
Druids regenerate more hp than damage that they can take in the early rounds, and that means nothing in the latest rounds. Just think about how much damage scales from the first round to say round 5-6 (about before the dragon). How do you balance that, it's impossible.
Meanwhile Predators have one of the most broken mechanic in the game, because with little effort they can mass execute due to items being able to process the trait's effect. They also require only 3 units to activate, that are all cost 1 and 2 again, and have no scaling. So they are just as strong in the first rounds as they are in the latest. The only difference is that in the first rounds they hardly can have all the items that make them disgustingly broken. And the cherry on top is that because they require just 3 units to activate their broken effect, they can also combine with poison in the latest rounds with SINGED, who can easily build Morellonomicon, preventing all opposing units both from HEALING and CASTING THEIR ABILITIES, all this while he's dishing huge amounts of splash damage, is immune to CC and can mess up opposing unit's targeting system... AND of COURSE, the mass executions going randomly because KogMaw has two Static Shivs.
If you play against someone who runs Predators, chances are that if you look up their profile on UTFT you'll find out that they play ONLY Predators, with few to NO EXCEPTIONS. The only exception that you might see is Olaf. These players would be fine with playing TFT with only Poison/Predators and Glacial/Berserkers.