The very core of Turtle Rock's Evolve revolves around the four versus one premise, and even though it's only been two months since we last saw it, the "one" side of things has since undergone some changes. The developers made some alterations to the monster's system to give increased freedom to the player.
Originally, the monster had a set of skills that was automatically added to with each evolution. This remained static, meaning that each new stage brought the exact same additional or increased powers. Now, the monster has a skill tree and is given three points upon evolving. Players can decide whether they want to make one or two abilities particularly powerful, or if they want a more well-rounded build that's able to chain weaker combos.
Unfortunately, we don't know first-hand how this translates to gameplay. The demo we saw at PAX East only put us in the shoes of the Hunters. It's unclear at this point if the changes will create any balance issues, but from an outsider's perspective, more choice and freedom is always a good thing.