I've seen numerous threads and posts calling out for some form of Player vs. Player combat, and I just wanted to share my thoughts on it.
First, the premise of the game is not one that really condones Player vs. Player combat. The story is that the Kamikui are rising again, and so the player assembles a team to fight them back. Nothing suggests that there is ill will between the Oni themselves. Why would the players be fighting each other? The point is to work together against a threat to the world, not fight amongst ourselves.
This idea is addressed a bit with the concept of Arena battles or even a Duel system, wherein only those who purposefully meet up under controlled circumstances come to test their strength and skill against each other. But the problem I have with that is, how would these kind of fights realistically go?
Consider this: a majority of players, especially those who've reached a higher level, direct their efforts and resources to maximizing their damage output. For example, putting all of their status points into Dexterity and equipping certain Magatama to reach the coveted 3000 affinity. Almost no one uses Magatama for the purpose the game presents them to be: equipment to boost defenses. Instead, the most commonly used Magatama increases affinity and skill damage, leaving players with a lot less defense than they could have.
What does all this mean? It means that, for a player, damage dealt far exceeds the damage they are capable of surviving. So imagine two "powerful" players fighting each other. The first one to land a clean hit is almost guaranteed to win. Yes, we have dodge-rolling and guarding, but is that really the test of skill you're looking for? A contest to see who can last longest dodging and blocking?
Also consider how predictable end-game skills and equipment are. A spear-user? Water Dragon, Ice Blossom. Bow-user? White Peacock, Icicle Arrow. There is a depressingly small amount of variety when it comes to these kind of things, so going into a fight with another player offers little surprise value. You can figure out their general strategy and fighting-style just by looking at them. And they'd know yours just as easily. What does it become, then? A staring contest as both players do their best to stay out of range of the other's skills.
So, who wins in Player vs. Player? Long-range fighters whose skills can target, leaving their opponent with no choice but to guard since dodging wouldn't work; players with unpredictable Ougi skills; and maybe spear-users who use Intimidate. That's about it, unless a player is actually willing to invest in their defenses.
Honestly, I feel the blame should go to the way Player vs. Environment is structured. There's little strategy involved. Gather the enemies, unleash area-attacks, repeat. There is little concern for taking damage because most Youkai don't get the opportunity to attack, meaning it's pretty pointless to work on defenses, but absolutely worth it to increase damage.
Those are just my thoughts on the idea of Player vs. Player. Leave any thoughts and comments below.