Well, PvP is more suited to MMORPGs that base their platform entirely on combat and level differentiation. In addition, there are interesting skills you have at your disposal such as swinging your sword a certain way or have an over-the-top arcane ability. All that good stuff and looks good when you do these things, it makes you feel powerful. There are a ton of actions your toon can do as far as fighting and going on defense. However, if you just bsae off a PvP with simply on snapping, biting, and scratching, it can get tedious. (Or if you're really into that sort of stuff, then, alright, all good.)
Now, with Feral Heart as a whole, it would have to be carefully thought through, that is if it was ever to be embedded into the game. Since this is more of sandox type game, it'd be odd to have a PvP, least in my opinion. It's like having a PvP for a game like Wolf Quest, it wouldn't exactly fit together.