The story so far in the game focuses on uniting people of different backgrounds together to face a more dangerous threat, so the arena style PvP really doesn't make a whole lot of sense in the context of the story. Just because it exists in the world doesn't mean it should exist as part of the narrative. We're supposed to be the heroes of light who vanquish the darkness, not each other.

It would make more sense to create separate minigames where people can pit themselves against one another in a kind of friendly sport than traditional arena PvP, and it would give the game something actually unique as opposed to just copy pasting the same stuff every other MMORPG has done in the last decade. It would also allow the developers to avoid having to rebalance the PvE abilities to fit a PvP environment, which can be problematic if they are left to affect both aspects of the game.