From what I've read there is a lot of freedom to choose your ultimates, your abilities and so on. While this seems good, surely that causes a lot of problems, namely in people being able to very easily min max. If you can just take the best 6 abilities in the game, why wouldn't you?
It seems really hard to balance this way, because you need to balance 10,000,000 builds while if you played with a more structured way, you would need to balance say 100,000 builds. Not saying you need to go full restricted classes and gear, but it seems like there is too much of a thing.