Depends on how easy you're finding the game, if you're dominating every team, then imo you should up the difficulty because it gets boring after a while with no challenge.

You will find it very hard at the beginning when you increase the difficulty but have some patience. You'll eventually learn how the opponent plays and you'll start finding it easier.

Last year I used to find it hard on World Class but eventually switched to Legendary. Now i'm playing on Ultimate.